Abstract:
A surgical obturator comprising an elongate shaft extending along an axis between a proximal end and a distal end includes a bladeless tip disposed at the distal end of the shaft. The tip has a blunt point and a pair of shorter side surfaces separated by a relatively longer pair of opposing surfaces to form in radial cross-section a geometric shape that has a longer length and relatively narrower width. The side surfaces and opposing surfaces terminate in end surfaces located proximally from the blunt point. The end surfaces extend radially outwardly from opposite locations of the outer surface. A conical surface facilitates initial insertion of the obturator and the geometric shape facilitates separation of consecutive layers of muscle tissue having fibers oriented in different directions and provides proper alignment of the tip between the layers of muscle.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/836,023 filed on Jul. 14, 2010 which is a continuation of U.S. patent application Ser. No. 10/514,313, now U.S. Pat. No. 7,758,603, which entered the U.S. National Phase on Nov. 12, 2004 from International Application No. PCT/2003/014924, filed May 13, 2003, which published in English as International Patent Publication WO 2003/096879 A3, which claims the benefit of U.S. Application No. 60/381,469, filed May 16, 2002. The disclosures of all of these applications are incorporated by reference in their entireties herein. 
    
    
     FIELD OF THE INVENTION 
     This invention generally relates to trocar systems including obturators and, more specifically, to blunt cone tip obturators. 
     BACKGROUND 
     Trocar systems have been of particular advantage in facilitating less invasive surgery across a body wall and within a body cavity. This is particularly true in the case of the abdominal surgery where trocars have provided working channels across the abdominal wall to facilitate the use of instruments within the abdominal cavity. 
     The trocar systems of the past typically include a cannula, which defines the working channel, and an obturator which is used to place the cannula across the abdominal wall. The obturator is inserted into the working channel of the cannula and then pushed through the abdominal wall with a penetration force of sufficient magnitude to result in penetration of the abdominal wall. Once the cannula is in place, the obturator can be removed. 
     In the past, obturators have been developed with an intent to provide a reduction in the force required for penetration. Sharp blades have typically been used to enable the obturator to cut its way through the abdominal wall. While the blades have facilitated a reduced penetration force, they have been of particular concern once the abdominal wall has been penetrated. Within the abdominal cavity, there are organs which need to be protected against any puncture by an obturator. 
     In some cases, shields have been provided with the obturators in order to sense penetration of the abdominal wall and immediately shield the sharp blades. These shielding systems have been very complex, have required a large amount of time to deploy, and have generally been ineffective in protecting the organs against the sharp blades. 
     Blunt-tip obturators have been contemplated with both symmetrical and asymmetrical designs. While the blunt tip tends to inhibit damage to interior organs, it also tends to increase the penetration force associated with the obturator. Thus, there is a need in the art for an improved bladeless obturator that reduces the force required to place the obturator across the abdominal wall. 
     SUMMARY 
     In accordance with the present invention, a blunt tip obturator similar to that described in international application No. PCT/US02/06759 further including a cone at its distal tip is disclosed with characteristics that reduce the force required to penetrate the abdominal wall. The addition of the cone also reduces the tendency for the abdominal wall and the peritoneum to deflect or “tent” during insertion of the obturator. The blunt cone tip obturator of the invention penetrates and twists radially from a distal end to a proximal end of the tip. The blunt cone tip obturator facilitates insertion with a reduced penetration force as the user moves the tip back and forth radially while applying an axial penetration force. The blunt cone tip obturator can be directed and inserted between the fibers and then rotated to provide increased penetration and fiber separation. 
     These and other features and advantages of the invention will become more apparent with a discussion of preferred embodiments in reference to the associated drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1 and 1   a  illustrate side views of a trocar system including a cannula with associated valve housing, and an obturator with a blunt cone tip extending through the working channel of the cannula to facilitate placement across the abdominal wall; 
         FIG. 2  is a side elevation view of the blunt cone tip of a preferred embodiment of the invention; 
         FIG. 3  is a side elevation view of the blunt cone tip taken along line  3 - 3  of  FIG. 2 ; 
         FIG. 4  is an end view taken along line  4 - 4  of  FIG. 2 ; 
         FIG. 5  is a radial cross-section view taken along line  5 - 5  of  FIG. 2 ; 
         FIG. 6  is a radial cross-section view taken along line  6 - 6  of  FIG. 2 ; 
         FIG. 7  is a radial cross-section view taken along line  7 - 7  of  FIG. 2 ; 
         FIG. 8  is a radial cross-section view taken along line  8 - 8  of  FIG. 2 ; 
         FIG. 9  is a radial cross-section view taken along line  9 - 9  of  FIG. 2 ; and 
         FIG. 10  is a schematic view illustrating each of the  FIGS. 4-9  super-imposed to facilitate an understanding of the blunt cone tip and its twisted configuration. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A trocar system is illustrated in  FIG. 1  and is designated by reference numeral  10 . This system includes a cannula  12 , defining a working channel  14 , and a valve housing  16 . The system  10  also includes an obturator  18  having a shaft  21  extending along an axis  23 . A handle  25  is disposed at a proximal end of the shaft at  21  while a blunt cone tip  27  is disposed at a distal end of the shaft  21 . The shaft  21  of the obturator  18  is sized and configured for disposition within the working channel  14  of the cannula  12 . With this disposition, the obturator  18  can be directed to penetrate a body wall such as the abdominal wall to provide the cannula  12  with access across the wall and into a body cavity, such as the peritoneal or abdominal cavity. The blunt cone tip  27  serves to direct the obturator  18  through the abdominal wall and the peritoneum, and can be removed with the obturator  18  once the cannula  12  is operatively disposed with the working channel  14  extending into the abdominal cavity. 
     In order to facilitate penetration of the abdominal wall by the trocar system  10 , a penetration force, represented by an arrow  34 , is typically applied along the axis  23 . It can be appreciated that the force required to penetrate the abdominal wall drops significantly once the wall is penetrated. Further application of the force  34 , even for an instant of time, can result in injury to organs within the cavity. Where the obturators of the past have included blades facilitating penetration of the abdominal wall, these blades have been particularly threatening and detrimental to the interior organs. 
     Consequently, in accordance with the present invention, the tip  27  is provided with a blunt cone configuration. Blunt tips have been used in the past to reduce any potential for damage to interior organs. However, these blunt tips have increased the amount of force  34  required for penetration of the abdominal wall. The blunt cone tip  27  of the present invention takes into account the anatomical configuration of the abdominal wall with an improved structural design and method of insertion. 
     To fully appreciate these aspects of this invention, it is helpful to initially discuss the anatomy associated with the abdominal wall. The abdominal wall typically includes a skin layer and a series of muscle layers. The muscle layers are each defined by muscle fibers that extend generally parallel to each other in a direction that is different for each of the layers. For example, fibers of a first muscle layer and a second muscle layer may extend in directions that are 45 degrees off of each other. 
     Having noted the directional nature of the muscle fibers, it can be appreciated that such a structure is most easily penetrated by an obturator having a blunt cone tip. The blunt cone tip also has a rectangular and twisted configuration so as to provide better movement between the muscle layers. That is, the blunt cone tip is capable of being moved generally parallel to and between the fibers associated with a particular muscle layer. As a result, the obturator of the present invention reduces the penetration force  34  required to push the obturator  18  through a particular layer. 
     As described earlier, the fibers of the muscle layers may be oriented at different angles to each other such that proper alignment of the tip  27  for penetration of one layer may not necessarily result in proper alignment for penetration of the next layer. For at least this reason, the obturator  18  has a blunt cone tip  27  to direct the obturator  18  through the different layers and a rectangular configuration that is twisted slightly so that penetration of a first layer begins to rotate the distal end of the blunt cone tip  27  into proper orientation for penetration of the next layer. 
     The twisted configuration of the blunt cone tip  27  also causes the blunt cone tip  27  to function with the mechanical advantage of a screw thread. With this configuration, a preferred method of placement requires that the user grip the handle  25  of the obturator  18  and twist it about the axis  23 . This twisting motion in combination with the screw configuration of the blunt cone tip  27  converts radial movement into forward movement along the axis  23 . Thus, the user applies both a forwardly directed force as well as a radial force to move the trocar system  10  in a forward direction. Since all of the force supplied by the user is not directed axially along the arrow  34 , this concept avoids the tendency of prior trocar systems to jump forward upon penetration of the abdominal wall. 
     The twisted configuration of the blunt cone tip  27  is most apparent in the side elevation views of  FIGS. 2 and 3 . In this embodiment, the blunt cone tip  27  comprises generally of eight surfaces: two opposing surfaces  50  and  52 , separated by two side surfaces  54  and  56 , two end surfaces  58  and  59 , a conical surface  60  formed in surfaces  50  and  52  around axis  23  and extending beyond end surfaces  58  and  59 , and a blunt surface  62 . A plane drawn through the axis  23  would show the tip  27  to be composed of two symmetrical halves. 
     The surfaces  50  and  52 , side surfaces  54  and  56 , and conical surface  60  generally define the cross section of the blunt cone tip  27  from blunt surface  62  to proximal end  61 . This configuration can best be appreciated with reference to the cross section views of  FIGS. 4-9 . In  FIG. 4 , the distal end of the blunt cone tip  27  is shown with a circle  64  having the smallest circular area and a rectangle  63  having the greatest length-to-width ratio. The rectangle  63  has a twisted, S-shaped configuration at end surfaces  58  and  59 . 
     As views are taken along progressive proximal cross sections, it can be seen that the circle  64  becomes larger and the rectangle  63  becomes less twisted, and the width increases relative to the length of the rectangle  63 . The spiral nature of the blunt cone tip  27  is also apparent as the circle  64  and rectangle  63  move counterclockwise around the axis  23 . This is perhaps best appreciated in a comparison of the circle  64  and the rectangle  63  in  FIG. 6  relative to that in  FIG. 5 . With progressive proximal positions, the circle  64  begins to expand with increasing circular area and the rectangle  63  begins to widen with a reduction in the ratio of length to width. The long sides of the rectangle  63  also tend to become more arcuate as they approach a more rounded configuration most apparent in  FIGS. 8 and 9 . That is, the circle  64  and the rounded rectangle  63  become more concentric with progressive proximal positions. Furthermore, the circle  64  expands at a lesser rate than the rectangle  63 , which eventually absorbs the circle  64  as shown in  FIGS. 8 and 9 . In these figures, it will also be apparent that the rotation of the rectangle  63  reaches a most counterclockwise position and then begins to move clockwise. This is best illustrated in  FIGS. 7-9 . This back and forth rotation results from the configuration of the side surfaces  54  and  56 , which in general are U-shaped as best illustrated in  FIGS. 2 and 3 . 
     The ratio of the length to width of the rectangle  63  is dependent on the configuration of the side surfaces  54  and  56 , which define the short sides of the rectangle  63  as well as the configuration of the surfaces  50  and  52 , which define the long sides of the rectangle  63 . Again with reference to  FIGS. 2 and 3 , it can be seen that the side surfaces  54  and  56  are most narrow at the end surfaces  58  and  59 . As the side surfaces  54  and  56  extend proximally, they reach a maximum width near the point of the most counterclockwise rotation, shown generally in  FIG. 8 , and then reduce in width as they approach the proximal end  61 . Along this same distal to proximal path, the surfaces  50  and  52  transition from a generally flat configuration at the end surfaces  58  and  59  to a generally rounded configuration at the proximal end  61 . 
     In the progressive views of  FIGS. 5-7 , the circle  64  is further designated with a lower case letter a, b or c, respectively; similarly, the rectangle  63  is further designated with a lower case letter a, b, c, d or e, respectively, in  FIGS. 5-9 . In  FIG. 10 , the circles  64 ,  64   a - 64   c  and the rectangles  63 ,  63   a - 63   e  are superimposed on the axis  23  to show their relative sizes, shapes and angular orientations. 
     A preferred method of operating the trocar system  10  benefits significantly from this preferred shape of the blunt cone tip  27 . With a conical configuration at the distal point and a rectangular configuration at a distal portion of the tip, the tip  27  appears much like a flathead screwdriver having a cone at its tip. Specifically, the blunt tip includes a conical structure extending outward from the end surfaces  58  and  59  that serves to direct the obturator through the abdominal wall and peritoneum. The cone tip has a radius of approximately 0.025″. The incorporation of the cone onto the rectangular configuration reduces the insertion force required to traverse the abdominal wall. An advantage of the obturator of the invention is it provides a safer and more controlled entry of the abdominal cavity. 
     It is preferable that the lengths of the end surfaces  58  and  59  are aligned parallel with the fibers of each muscle layer. With this shape, the blunt cone tip can be used to locate or pinpoint a desired location and penetrate the abdominal wall. A simple back and forth twisting motion of the blunt cone tip tends to separate the fibers along natural lines of separation, opening the muscle layer to accept the larger diameter of the cannula  12 . By the time the first layer is substantially penetrated, the conical and twisted configuration of the blunt cone tip  27  directs and turns the rectangle  63  more into a parallel alignment with fibers in the next layer. Again, the blunt cone tip facilitates penetration, and the twisting or dithering motion facilitates an easy separation of the fibers requiring a significantly reduced penetration and insertion force along the arrow  34 . 
     It should be further noted that the blunt cone tip  27  is bladeless and atraumatic to organs and bowel within the peritoneal or abdominal cavity. The blunt cone tip  27  also minimizes tenting of the peritoneum and allows for a safe entry. The device is typically used in conjunction with the cannula  12  to create an initial entryway into the peritoneal cavity. The obturator  18  is first inserted through the valve housing  16  and into the cannula  12 . The entire trocar system  10  is then inserted through the abdominal wall and into the peritoneal cavity. Once the cannula  12  is properly placed, the obturator  18  can be removed. 
     The invention facilitates a unique method of penetrating and separating tissue and could apply to any object with a blunt cone tip and generally flat sides. When inserted into the peritoneum the blunt cone tip requires very little area to move safely between tissue and muscle fibers. The device can then be rotated in alternating clockwise and counterclockwise directions while the downward penetration force is applied. When rotated in alternating directions, the tissue is moved apart and a larger opening is created for a profile of greater cross sectional area to follow. This process continues with safety as the device enters the peritoneal cavity and moves to its operative position. 
     When the cannula  12  is ultimately removed, the size of the opening left in the tissue is minimal. Importantly, this opening is left sealed due to a dilating effect caused by the mere separation of fibers. Since there are no blades or sharp edges to cut muscle fiber, the healing process is significantly shortened. 
     The obturator  18  can be constructed as a single component or divided into multiple components such as the shaft  21  and the blunt cone tip  27 . If the obturator  18  is constructed as a single component, it may be constructed of either disposable or reusable materials. If the obturator  18  is constructed as two or more components, each component can be made either disposable or reusable as desired for a particular configuration. In a preferred embodiment, the obturator is constructed as a single component made from a reusable material such as metal (e.g., stainless steel) or an autoclavable polymer to facilitate re-sterilization. 
     In another embodiment of the invention, the blunt cone tip  27  can be coated or otherwise constructed from a soft elastomeric material. In such a case, the material could be a solid elastomer or composite elastomer/polymer. 
     The shaft  21  of the obturator  18  could be partially or fully flexible. With this configuration, the obturator  18  could be inserted through a passageway containing one or more curves of virtually any shape. A partially or fully flexed obturator  18  could then be used with a flexible cannula  12  allowing greater access to an associated body cavity. 
     The obturator  18  could also be used as an insufflation needle and provided with a passageway and valve to administer carbon dioxide or other insufflation gas to the peritoneal cavity. The obturator  18  could also be used with an insufflation needle cannula, in which case removal of the obturator  18  upon entry would allow for rapid insufflation of the peritoneal cavity. 
     It will be understood that many modifications can be made to the disclosed embodiments without departing from the spirit and scope of the invention. For example, various sizes of the surgical device are contemplated as well as various types of constructions and materials. It will also be apparent that many modifications can be made to the configuration of parts as well as their interaction. For these reasons, the above description should not be construed as limiting the invention, but should be interpreted as merely exemplary of preferred embodiments.