Abstract:
In endoscopic surgery, a retractor having independently spreadable retractor blades mounted at the distal end of a tube is introduced percutaneously. A balloon dissector is passed through the tube and expanded. Following dissection by expansion of the balloon, the balloon is contracted, the tube is advanced, and the dissected tissue is spread by moving the blades apart from each other. The balloon dissector is withdrawn and another instrument is then introduced to carry out surgery on the anatomical structure exposed by the dissection and spreading steps.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a division of patent application Ser. No. 11/639,869, filed Dec. 15, 2006, now U.S. Pat. No. 8,052,710, granted on Oct. 19, 2011. The disclosure of application Ser. No. 11/639,869 is here incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to surgery, and particularly to an endoscopic method for dissection and retraction of tissue, and to instruments for use in carrying out the method. 
     BACKGROUND OF THE INVENTION 
     In surgery, adhesions and scar tissue, formed in a patient&#39;s thoracic or abdominal cavity as a result of previous surgery, infection or trauma, frequently cause difficulties in locating, and gaining access to, the internal organs or structures that require repair or removal. For example, adhesions frequently cause problems in anterior and anterolateral access to the spinal column or the content of the abdominal cavity. 
     Typically, a surgeon releases adhesions manually, using a gloved finger. However, when a gloved finger is used, it is not possible to visualize the adhesions, and unnecessary bleeding, and tearing, or damage to the normal anatomy, almost inevitably occurs. In addition, access to certain organs requires the identification and separation of two muscle groups through their anatomical planes. 
     An endoscopic balloon tissue dissector can be used to achieve the above objectives, and various instruments incorporating inflatable balloons have come into use for tissue dissection. The balloon, incorporated at the distal end of an endoscopic instrument, is inserted between adjacent tissue layers, and inflated to separate those layers. Alternatively, for dissection with visualization, some surgeons have used an “optical trocar,” which comprises a tube having a system of lenses or a bundle of optical fibers for transmitting an image from the distal end of the tube to an eyepiece or to an electronic video monitor. 
     More recently, a surgical dissector has been developed which combines features of the balloon dissector and the optical trocar. Such an instrument is described in U.S. Pat. No. 5,607,441. In that instrument, a transparent, inflatable, dissecting balloon is provided at the distal end of a shaft, and an optical instrument, extending through the shaft into the interior of the balloon, enables the surgeon to visualize the dissection as it takes place. 
     Despite the advances in endoscopic surgery exemplified by U.S. Pat. No. 5,607,441 and numerous other patents, there remains a need for instrumentation that can achieve dissection of tissue and provide optimal access to a surgical site with minimal trauma to the patient. 
     BRIEF SUMMARY OF THE INVENTION 
     In a preferred embodiment of the invention, the instrument comprises an elongated tube having proximal and distal ends, and an internal passage for insertion of an instrument through the tube. Plural retractor blades, preferably two opposed retractor blades, extend distally from a location adjacent the distal end of the tube, and are movable radially with respect to the central axis of the tube by adjuster rods. An adjuster rod is connected to each blade, extends proximally at least part way through the tube, and is accessible at a location adjacent the proximal end of the tube for independent radial adjustment of the retractor blades. 
     Preferably, each of the retractor blades is pivoted at a pivot location adjacent the distal end of the elongated tube, and the adjuster rod connected to each blade is connected at a location spaced from the pivot location of the blade, so that it can effect radial adjustment by pivoting the blade to which it is connected. 
     The elongated tube preferably has a substantially cylindrical external surface substantially symmetrical about its central axis, and the internal passage is also substantially symmetrical about the central axis. In this embodiment, the plural retractor blades consist of two retractor blades in opposed relationship to each other, and the blades are adjustable to positions in which they are substantially within an axial projection of the substantially cylindrical external surface of the tube but substantially entirely external to an axial projection of the internal passage. Consequently, an expandable balloon on an end of a balloon dissector can be inserted through the internal passage so that it can project distally beyond the blades, and withdrawn, while the blades are in the above-mentioned positions. 
     The blades are preferably formed so that they have outer, tissue-engaging, surfaces which are convex throughout substantially their entire axial lengths in cross-sectional planes to which the central axis is perpendicular, and inner surfaces which are concave throughout substantially their entire axial lengths in the same cross-sectional planes. 
     The adjusting rods preferably have external screw threads threadingly engaged with internal screw threads fixed to the tube, and are preferably separated from the internal passage by a second tube defining the internal passage. 
     Another aspect of the invention is an instrument in which the tube having retractor blades at its distal end is combined with a balloon dissector. More particularly, this combined instrument comprises an elongated first tube having proximal and distal ends, the tube having an internal passage for insertion of an instrument through the tube. The first tube has a substantially cylindrical external surface substantially symmetrical about an axis of elongation of the tube, and the internal passage is also substantially symmetrical about the same axis. Two retractor blades, in opposed relationship to each other, extend distally from locations adjacent the distal end of the first tube and are movable radially with respect to the axis tube&#39;s axis of elongation. An adjuster rod is connected to each blade, and each rod extends proximally at least part way through the first tube, and is accessible at a location adjacent the proximal end of the first tube for independent radial adjustment of the retractor blades. The balloon dissector comprises an elongated second tube having proximal and distal ends, and an expandable balloon at the distal end of the second tube. The blades are adjustable to positions in which they are substantially within an axial projection of the external surface of the first tube but substantially entirely external to an axial projection of the second tube and any external channel-defining wall on the second tube. The second elongated tube, that is, the tube of the balloon dissector, extends through the internal passage of the first elongated tube from a location proximal with respect to the proximal end of the first elongated tube to a location at which at least part of the expandable balloon is distal with respect to the blades. Thus, the balloon can be expanded to dissect tissue located in distal relation to the blades, and then contracted to permit movement of the blades into a space created by the dissection of tissue by the balloon. Then spreading of the tissue can be effected by adjustment of the blades, and, following withdrawal of the second elongated tube, another instrument can be introduced through the internal passage of the first tube for surgery on the anatomical structure exposed by dissection and spreading. 
     Here again, each of the two opposed retractor blades is preferably pivoted at a pivot location adjacent the distal end of the elongated tube, and the adjuster rod connected to each blade is connected at a location spaced from the pivot location of the blade so that it can effect radial adjustment by pivoting the blade to which it is connected. 
     The balloon of the balloon dissector is preferably transparent, and a shaft, extending through the second elongated tube to a location within the balloon, comprises an image transmitter for transmitting a visual image of a patient&#39;s anatomical structure immediately external to the balloon, through the elongated first tube, to a location external to the patient. 
     Still another aspect of the invention is a surgical method which can be carried out using the above-described instruments. The method comprises at least the following steps. A first step is the percutaneous introduction of an elongated first tube having proximal and distal ends, the tube having an internal passage for insertion of an instrument through the tube, and two retractor blades in opposed relationship to each other and extending distally from the distal end of the tube. Then, a balloon, connected to a distal end of an elongated second tube extending through the internal passage of the first tube, is disposed at a location distal with respect to the retractor blades, and expanded by introducing a fluid, which may be either a liquid or a gas, into the interior of the balloon. By expanding the balloon the surgeon can dissect tissue at the location of the balloon. Afterwards, by at least partially contracting the balloon, and moving the elongated first tube in the distal direction, the surgeon can cause the blades to move into the space created by the dissection of tissue using the balloon. The dissected tissue can then be spread by moving at least one of the blades apart from the other before, during, or after withdrawal of the elongated second tube from the internal passage of the elongated first tube. After withdrawal of the second tube, and, while using the blades to maintain the dissected tissue in a spread condition, another instrument can be introduced through the internal passage of the first tube for surgery on anatomical structure exposed by the dissection and spreading steps. 
     If the balloon is transparent, during the step of expanding the balloon, tissue at the location of the balloon can be visualized through the balloon by transmitting an image of tissue at the location of the balloon through an image transmitter in a shaft extending through the elongated second tube to the interior of the balloon. 
     The image transmitter can also be used for visualization during expansion of the retractor blades. If the blades are independently adjustable, in the spreading step, at least one blade can be moved apart from the other blade independently of movement of the other blade. In this way, tissue can be spread for access to a surgical site with minimal trauma to the patient. 
     The step of percutaneously introducing an elongated first tube can be carried out by a series of steps including the steps of passing an obturator having a blunt tip through a patient&#39;s skin, passing a hollow cannula over the obturator, withdrawing the obturator, and introducing the elongated first tube through the hollow cannula. The obturator can have a guide-wire channel, and can be introduced by passing it over a pointed guide wire previously passed through the patient&#39;s skin. 
     Other details and advantages of the invention will be apparent from the following detailed description when read in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an elevational view of a guide wire which can be used in the surgical dissection of tissue in accordance with the invention; 
         FIG. 2  is an elevational view, partly in section, of a blunt-tipped cannula, having a longitudinal guide wire-receiving channel; 
         FIG. 3  is an elevational view, partly in axial cross-section, of a hollow cannula; 
         FIG. 4  is a shortened axial section of an elongated first tube in accordance with the invention, the tube having retractor blades shown in positions in which they are substantially within an axial projection of the external surface of the tube; 
         FIG. 5  is a shortened axial section, similar to  FIG. 5 , but showing one of the retractor blades in a spread condition; 
         FIG. 6  is a perspective view of the first elongated tube, showing the retractor blades in the same condition as shown in  FIG. 4 ; 
         FIG. 7  is a shortened axial section of an elongated second tube, having a dissecting balloon at one end, and an image transmitting shaft extending through the tube to the interior of the balloon; 
         FIG. 8  is a shortened axial section showing the second tube extending through the first tube; 
         FIG. 9  is a schematic diagram showing the balloon carrying out a dissection of tissue; 
         FIG. 10  is a schematic diagram, similar to  FIG. 9 , showing the retractor blades spreading tissue previously dissected by the balloon; and 
         FIG. 11  is a shortened axial section, similar to  FIG. 7 , showing an elongated second tube having an auxiliary channel. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  shows a guide wire  12 , which is typically inserted through an incision in a patient&#39;s skin and advanced toward the site at which surgery is to be performed. For example, in the case of spinal surgery performed using a posterior or posterolateral approach, the guide wire can be inserted through the patient&#39;s skin, using fluoroscopic guidance to avoid tissue damage. With the guide wire  12  in place, an obturator  14 , as shown in  FIG. 2 , is passed over the guide wire. The obturator is elongated, has a blunt tip  16 , a preferably circular, cylindrical exterior wall  18 , and a centrally located longitudinal channel  20  for receiving the guide wire  12 . As an alternative, a solid obturator can be used without a guide wire, especially in cases where the depth to which the obturator is inserted is small. 
     With the obturator  14  in place, a cannula  22 , as shown in  FIG. 3  can be passed over the exterior of the obturator. The cannula can be manipulated by a handle  24 , which can also be rigidly attached by a support arm to the operating table or another fixed structure. A set screw  26  is provided in the wall of the cannula for holding the tube of a retractor in fixed relation to the cannula so that the retractor does not slide forward or backward during surgery. 
     As shown in  FIG. 4 , the retractor  28  comprises an elongated outer tube  30  having a proximal end  32 , a distal end  34 , and a substantially cylindrical, preferably circular, outer surface symmetrical about a central axis extending lengthwise of the tube. An inner elongated tube  36 , which is coaxial with the first tube, is located inside the first tube. The inner tube  36  is also preferably symmetrical about the axis of tube  30 , and its inner wall, which is preferably also substantially cylindrical and circular, forms an internal passage  38 , though which another instrument can be inserted. 
     The inner and outer tubes are held in fixed relationship to each other by a ring  40 , and by other connecting elements (not shown). 
     Two retractor blades,  42  and  44 , extend in the distal direction from the distal end  34  of tube  30  in opposed relationship to each other. The blades are pivoted on pins  46  and  48 , respectively, and are independently movable about their pivot axes so that one or both can be moved radially outward relative to the central axis of the tubes. Blade  42  is shown pivoted outward in  FIG. 5 , while blade  4  remains in its original position. 
     The shapes of the blades can be better appreciated from  FIG. 6 , in which it can be seen that the blades have convex outer surfaces and concave inner surfaces. That is, the blades have outer, tissue-engaging, surfaces which are convex throughout substantially their entire axial lengths in cross-sectional planes to which the axis of the tubes is perpendicular, and inner surfaces which are concave throughout substantially their entire axial lengths in the same cross-sectional planes. Because of the concave/convex shapes of the blades, when they are in the positions depicted in  FIG. 4 , they are located substantially entirely between axial projections of the inner passage and the outer wall of tube  30 . More particularly, the blades are adjustable to positions in which they are substantially within an axial projection of the substantially cylindrical external surface of the elongated first tube, but substantially entirely external to an axial projection of the internal passage  38 . When the blades are in the positions shown in  FIG. 4 , it is possible for the retractor to be inserted through the cannula  3  ( FIG. 3 ), and it is also possible for an instrument having a width nearly equal to the width of passage  38  to be inserted, without interference, through passage  38  and through the space between the blades. 
     The blades are adjustable independently by rods  50  and  52 , which extend through the space between tubes  30  and  36 . The rods have non-circular proximal end extensions  54  and  56  near the proximal end  32  of the outer tube  30 . These extensions are engageable by a key  58  ( FIG. 5 ) for rotation of the rods to adjust the positions of the blades  42  and  44 . Threads  60  and  62 , formed on the rods, are threadingly engaged with internal threads formed in ring  40 , which is fixed to both tubes. A ball, formed at the distal end of each rod, fits between upper and lower plates formed on the blade with which the rod is associated at a location spaced a short distance from the pivot pin. For example rod  50  is provided with a ball  64 , and extends through a hole in upper plate  66  of blade  42  and fits in a space between the upper plate  66  and a lower plate  68 . Upon rotation of the rod in one direction, the rod will pull up on plate  66 , causing the blade  42  to pivot outward. Upon rotation of the rod in the opposite direction, the rod will push on plate  68  causing the blade  42  to pivot inward. The pitch of the threads of the threaded rods and the ring is preferably sufficiently small that the blades cannot be moved about their pivots by forces applied directly to the blades. 
     The balloon dissector  70 , shown in  FIG. 7  comprises a second tube  72 , the outer wall of which is preferably in the form of a circular cylinder having a diameter slightly less than that of the inner wall  38  of tube  36  ( FIG. 4 ). Attached to the distal end  74  of the tube  72  is an expansible, preferably transparent, elastomeric balloon  76 , which can be used to dissect tissue when expanded by introduction of a liquid or gas through tube  72 . The balloon can be fabricated so that it expands uniformly, or so that it expands non-uniformly in a desired direction. A wire  78 , which is flexible, but considerably more rigid than the balloon is located inside the balloon and also attached to the distal end of tube  72 . The wire  78  aids the advancement of the unexpanded balloon into a patient&#39;s tissue, and is preferably made from metal or a fiber-reinforced polymer. 
     An image-transmitting device  80  is inserted through tube  72 , and comprises an elongated shaft  82 , the distal end  84  of which preferably extends beyond the distal end  74  of the tube into the interior of the balloon  78 . The proximal end of the image transmitting device is provided with threads  86 , which are threaded into the proximal end of the tube  72 . In practice, tube  84  can be an optical telescope having a series of lenses arranged to focus an image onto a television camera  88 , which is connected through a cable  90  to a monitor (not shown). Illumination at the distal end of the image transmitting device can be provided through an optical fiber bundle (not shown). 
     There are many alternatives to the image transmitting device described above. In one alternative version, the camera can be replaced by an eyepiece for direct viewing through the telescope. An optical fiber bundle can be used to transmit an image through shaft  82  either to a camera or to an eyepiece. As a further alternative, the camera can be situated at the distal end of shaft  82 . In all cases, however, the image transmitter, when used in conjunction with the transparent balloon, enables the surgeon to visualize the tissue as it is dissected. 
     The balloon is expanded by the introduction of a fluid, preferably a normal saline solution, through valve  92 , and through tube  72 , into the interior of the balloon. Valve  94  is used for the removal of air bubbles from the saline solution, and may also be used for drawing saline solution out of tube  72 . 
       FIG. 8  shows the dissecting instrument of  FIG. 7  inserted through the central passage of the retractor of  FIGS. 4 and 5 . At least part of the balloon  76  extends beyond the distal tips of the retractor blades  42  and  44 . In this figure, it will be seen that tube  72  of the dissecting instrument fits through passage  38  of the retractor, and between the retractor blades  42  and  44 , even though the retractor blades are not spread apart. When the blades are in the position shown, they are situated substantially entirely outside an axial projection of the inner wall of passage  38 , but substantially entirely inside an axial projection of the outer wall of the outer tube. Consequently, with the blades in the position shown in  FIG. 8 , which is the same as the blade position shown in  FIGS. 4 and 6 , the retractor can be inserted through the hollow cannula  22  of  FIG. 3 . Moreover, without spreading the blades apart from each other, the balloon dissector  70  can be introduced through the passage  38 , so that the balloon passes through the space between the blades to a location distal with respect to the tips of the blades, as shown in  FIG. 8 . Of course, the balloon dissector can be inserted either before or after the retractor is inserted through the cannula. However, ordinarily, the retractor will be inserted partway through the cannula, and temporarily locked in place by set screw  26  ( FIG. 3 ), before the balloon dissector is inserted through the retractor. 
     As shown in  FIG. 9 , the cannula  22  is shown extending through an opening in the abdomen  96  of a patient  98 , in a surgical operation on the patient&#39;s spine  100 . The retractor  28  is shown positioned so that the retractor blades are inside the cannula  22 , but the balloon dissector  70  protrudes through the distal opening of the cannula. The balloon is used to dissect tissue to gain access to the patient&#39;s spine, and is shown expanded by the introduction of fluid into its interior. The surgeon can observe the dissection visually on a monitor connected to the image transmitting device that extends into the interior of the balloon. 
     After completion of dissection by means of the balloon, the balloon is allowed to contract, by exhaustion of expansion fluid, to a size such that the retractor can be moved forward over the balloon without spreading the retractor blades. The balloon dissector can then be withdrawn, and the retractor blades  42  and  44  are then spread apart from each other as shown in  FIG. 10 . Since the blades are adjustable independently, they can be spread by adjustment of both blades, or by adjustment of either blade by itself. With the cannula rigidly supported on a support arm (not shown) and the retractor locked in place by the set screw  26  ( FIG. 3 ), the surgeon can introduce other instruments through the central channel of the retractor, visualizing the surgical site, in this case the patient&#39;s spine, through another image transmitting device, which can extend through the retractor, or which can be introduced through another portal. 
     As will be apparent, the balloon dissector can be used to remove adhesions and dissect tissue for initial access to the surgical site, and the retractor blades can be used to expand and/or maintain the space opened up by dissection, to allow other surgical instruments to be introduced. 
     Various modifications can be made to the instrumentation described above. For example, although the retractor blades described herein are pivoted, as an alternative, linkage structures can be provided so that the retractor blades remain parallel to each other when expanding. The retractor blades can be formed in various shapes other than the shape illustrated, and the retractor can also have more than two blades. Moreover, although the retractor blades are preferably moved by a screw mechanism such as the mechanism shown in  FIGS. 4 and 5 , the blades can be controlled by various other mechanisms, such as a rack and pinion mechanism. The connection between an adjusting rod and a pivoted blade can be made by providing two balls on the rod, one ball being above, and the other being below, plate  66  ( FIG. 4 ). The cross-sectional shape of the inner and outer tubes can be non-circular. For example, the tubes can be oval-shaped in transverse cross-section. The instruments can, of course, be made in various diameters and lengths. 
       FIG. 11  shows a balloon dissector similar to that in  FIG. 7 . In  FIG. 11 , parts corresponding to those in  FIG. 7  are identified by the same reference numbers followed by the prime (′) symbol. As shown in  FIG. 11 , the balloon dissector can be provided with a wall  102  defining a separate working channel having a proximal opening  104  and a distal opening  106  adjacent to the balloon  76 ′, and outside the balloon, for insertion of a variety of instruments, such as instruments for tissue resection, biopsy, or hemostasis. The separate working channel can also be used for introduction of saline solution to clean blood stains the exterior surface of the balloon so that they do not interfere with clear visualization by the surgeon. A rubber cap (not shown) can also be provided at the proximal end of the additional working channel so that saline solution can be injected under pressure. The separate working channel is preferably, but not necessarily, provided on the outside of the tube  72 ′. When the separate working channel is on the outside of the tube, the retractor blades should be positionable so that they are entirely within an axial projection of the retractor tube, but entirely outside an axial projection of the structure consisting of the tube  72 ′ and the channel-defining wall  102  of the balloon dissector, so that the balloon dissector can pass between the blades before the blades are spread apart from each other. 
     Still other modifications may be made to the apparatus and method described above without departing from the scope of the invention as defined in the following claims.