Patent Publication Number: US-2007118167-A1

Title: Traction trocar apparatus and method

Description:
BACKGROUND OF THE INVENTION  
      1. Field of Invention  
      This invention relates generally to trocar systems and more specifically to obturator apparatus and methods for placing a trocar cannula across a body wall  
      2. Discussion of the Prior Art and Related Technology  
      It is generally well known that holes can be created through body tissue either by cutting the tissue or by mechanically parting the tissue along lines of weakness. Where tissue is cut, it is severed along a line, which is determined by the direction of the cutting implement. Where tissue is parted, it separates along natural tissue planes such as those defined by muscle fibers or differing layers of tissue such as skin and muscle. Tissue that is mechanically separated tends to heal better than tissue that is cut with tissue that is mechanically separated the healing process requires only that the affected tissues re-approximate each other with cut tissue, and in particular muscle fibers, the healing process must reconstruct the damaged tissue, often with resultant scaring and incomplete reconstruction. It has been shown for laparoscopic surgery in particular, that trocar wound sites of 10 millimeters in diameter and higher, made by cutting obturators, require suturing to prevent incisional hernias from occurring. It has also been shown that where the same size would site is created by expanding or parting the wound from a cut of 3 millimeters, for example, that the wound site does not require stitching and tends to heal faster.  
      For laparoscopic surgery there is a requirement that instrument ports in the form of cannulas be placed in the patient&#39;s abdominal wall. These cannulas are then used as access ports for the surgeon to place instruments such as scissors and graspers. In the past these cannulas have been introduced by using a sharp cutting obturator, placed within the cannula, to cut a line or hole for, advancing the cannula through the abdominal wall. The obturator is then removed from the cannula and the cannula is left in place for the duration of the surgery.  
      For most surgeries the cutting obturator is only used after the abdomen has been insufflated with carbon dioxide gas. There is then separation between the abdominal wall and the underlying anatomical structures and organs. Even with this separation, however; there is a risk that the patient will be injured by the sharp cutting tip of the obturator as it breaks through the abdominal wall. To help resolve this issue a variety of mechanical shielding mechanisms have been employed to cover the cutting element once it breaks through the abdominal wall. It has been noted and observed that even with these mechanical shield mechanisms that the risk is not completely eliminated and that the rigid shields themselves can cause damage to internal organs and structures.  
      Other methods have been used as well. For example, optical trocars have been provided with a cleat plastic cutting tip. This allows the surgeon to view the tissue layers as they are cut, and in principle to better, control the timing of insertion forces. These plastic tips, however, are not as sharp as the metal bladed variety and therefore require a higher insertion force which in turn increase abdominal wall distortion. This distortion or tenting brings the obturator tip into closer proximity with the internal organs and increases the chances for potential damage. The wound created by such a device is still a cut and not a mechanical separation, as it still suffers from the above-mentioned disadvantages.  
      Another manufacturer employs a multistage system whereby a sheath is inserted over a veress needle. The needle is then removed and a conical obturator, placed inside a cannula, is inserted through the sheath thereby expanding it to the desired cannula size. The obturator is then removed leaving the cannula in place. This offers the advantage of a smaller initial incision with the veress needle. However, the needle still presents a risk to internal organs, and the system is more expensive and complex than those associated with the cutting obturator devices.  
      In all of these systems of the past, a cutting element is employed to either create the final size of the wound site or to make a smaller initial wound site that is then expanded to the final size. The use of sharp cutting elements common to all systems presents an unavoidable risk to the patient.  
     SUMMARY OF THE INVENTION  
      These deficiencies of the prior art are overcome with the present invention which provides for the parting rather than cutting of tissue, and, the use of opposing radial forces which precede the tip of the obturator shaft. After the tissue is parted, it is drawn proximally along the outer surface of the shaft as the shaft is moved distally through the body wall. The resulting counter forces can produce a net proximal force on the body wall with a minimal distal or penetration force.  
      In a preferred embodiment a tubular mesh sleeve is initially disposed in the hollow shaft of the obturator. This sleeve is pulled out of a hole at the tip of the obturator shaft and drawn radially and proximally along the outer surface of the shaft. The mesh sleeve inverts at the distal tip facilitating its movement interiorly of the shaft and its traction with the parted tissue exteriorly of the shaft.  
      In one aspect of the invention, an apparatus is provided for creating an opening through body tissue. The apparatus includes a shaft having an axis and a channel extending axially between a proximal end and a distal end. The shaft has a distal tip and a hole in the tip communicating pith the channel of the shaft. Portions of the tip define a leading surface of the tip. Means is disposed along this leading surface and is moveable relative to the tip for creating generally opposing forces on the body tissue which tend to part the body tissue and thereby create the opening through the body tissue.  
      In another aspect of the invention, a surgical instrument is used for creating an opening through an abdominal wall retaining internal organs. The instrument includes a shaft having an outer surface and a tip. A sheath initially contacting the body tissue generally at a point extends proximally from the point along the outer surface of the shaft. The shaft is operable to create a distal force on the body tissue while the sheath is operable to create a proximal force on the body tissue. The proximal force is greater than the distal force in order to create a net proximal force on the abdominal wall tending to separate the abdominal wall from the internal organs as the opening is created.  
      In another, aspect of the invention, a flexible sheath having a tubular configuration extends from an axial channel of the shaft through the distal tip of the shaft. A handle is attached to the sheath exteriorly of the shaft and is moveable proximally relative to the shaft to withdraw the sheath from the channel and to progressively invert the sheath at the tip of the shaft.  
      In another aspect of the invention, the shaft of the surgical instrument has a tubular configuration with an outer surface, an axial channel, and a distal tip. At least one flexible traction tread is carried within the axial channel and extends outwardly of the shaft at the distal tip. A handle attached to the traction tread exteriorly of the shaft is moveable proximally to withdraw the traction tread distally through the distal tip.  
      An associated method of operation includes even further aspects of the invention. For example, a method for creating an opening in body tissue includes the steps of providing opposing traction treads extending from the axial channel of the shaft outwardly through the hole in the tip of the shaft. The body tissue is contacted with the traction treads at the tip of the shaft and the traction treads arc moved radially outwardly from the hole in the tip. During this moving step, the body tissue is engaged at the tip to produce parting forces on the body tissue tending to separate the body tissue and thereby create the opening through the body tissue.  
      In another method of operation, first and second cannulas are inserted through body tissue by providing an obturator having a shaft with an outer surface and a traction tread moveable relative to the outer surface. Placing the obturator in the first cannula, the body tissue is engaged with the tread and the tread is moved relative to the outer surface of the shaft to facilitate penetration of the body tissue by the shaft and the first cannula. The obturator is then removed from the first cannula and placed in the second cannula where again the traction thread engages the tissue and facilitates penetration of the body tissue by the shaft in the second cannula. Removing the obturator from the second cannula leaves both the first cannula and the second cannula operatively disposed across the body wall.  
      In another method associated with the invention, removal of a trocar cannula from a body wall is facilitated by placing a mesh sleeve between the cannula and the body wall. The sleeve is provided with properties which exert a radial force on the cannula tending to resist removal of the cannula from the body wall. However, an axial force can be applied to the sleeve to reduce the radial force of the sleeve on the cannula. During this step of applying the axial force, the cannula can be removed from the body wall.  
      In a method for inserting an obturator, the obturator is provided with a shaft having an outer surface and a traction tread moveable along the outer surface of the shaft. The tread is carried within the shaft. As the obturator is moved through the body wall, a first force is applied to the obturator in a first direction and a second force is applied to the obturator in a second generally opposing direction. As the obturator is moved distally relative to the body wall, it engages wall portions which face the outer surface of the shaft and pulls those wall portions proximally along the shaft.  
      These and other features and advantages of the invention will be better understood with reference to preferred embodiments of the concept and reference to the associated drawings. 
    
    
     DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a side elevation view of a patient with insufflated abdomen and trocars in the process of being placed using the trocar system of the present invention;  
       FIG. 2  is a side elevation view of a prior art trocar system involving an incision and blunt tip obturator;  
       FIG. 3  is a side elevation view of a prior art trocar system involving an obturator with cutting wings;  
       FIG. 4  is a side elevation view of a prior art trocar system including a cutting tip;  
       FIG. 5  is a side elevation vies of the system of  FIG. 4  invading an interior organ;  
       FIG. 6  is a side elevation view of the system of the present invention including an inverting sheath operable with counter forces which can produce a net proximal force on the body wall;  
       FIG. 7  is a side elevation view of an embodiment including a single traction tread;  
       FIG. 8  is a radial cross section view taken along lines  8 - 8  of  FIG. 7 ;  
       FIG. 9  is a side elevation view of an embodiment including a pair of opposing traction treads;  
       FIG. 10  is a radial cross section view taken along lines  10 - 10  of  FIG. 9 ;  
       FIG. 11  is a side elevation view of an embodiment having more than two traction treads equally circumferentially spaced;  
       FIG. 12  is a radially cross section view taken along lines  12 - 12  of  FIG. 11 ;  
       FIG. 13  is a side elevation view wherein the traction tread is radially continuous and forms a tube or traction sheath;  
       FIG. 14  is an axial cross section view taken along lines  14 - 14  of  FIG. 13 ;  
       FIG. 15  is an end view taken along lines  15 - 15  of  FIG. 14 ;  
       FIG. 16  is a side elevation view of a further embodiment of the obturator wherein opposing traction treads are axially continuous;  
       FIG. 17  is an axial cross section view taken along line  17 - 17  of  FIG. 16 ;  
       FIG. 18  is an end view taken along line  18 - 18  of  FIG. 17 ;  
       FIG. 19  is a front elevation view similar to  FIG. 16  and illustrating an embodiment including axially continuous traction treads;  
       FIG. 20  is an axial cross section view taken along lines  19 - 19 ;  
       FIG. 21  is an end view taken along lines  21 - 21  of  FIG. 20 ;  
       FIG. 22  is a side elevation view of the embodiment of  FIG. 13  placed in initial contact with an abdominal wall to produce opposing parting forces;  
       FIG. 23  is a side elevation view similar to  FIG. 22  and showing the obturator with the abdominal wall being drawn upwardly onto the cannula of the trocar system;  
       FIG. 24  is a side elevation view similar to  FIG. 23  and illustrating the abdominal wall fully parted by the trocar cannula;  
       FIG. 25  is a side elevation view of the embodiment illustrated in  FIG. 24  showing the abdominal wall drawn proximally onto the trocar cannula by the traction sheath;  
       FIG. 26  is the side elevation view of the system illustrated in  FIG. 25  with the traction sheath fully deployed to maintain traction between the abdominal wall and the cannula, and with the obturator removed to vacate the working channel of the cannula;  
       FIG. 27  is a side elevation view of the system illustrated in  FIG. 26  with the trocar cannula removed from the traction sheath;  
       FIG. 28  is a side elevation view of the system illustrated in  FIG. 27  showing the traction sheath removed from the opening leaving parted surfaces to promote healing;  
       FIGS. 29-32  illustrate a series of side elevation views showing progressive steps for operating an embodiment wherein the inverting sheath is disposed outwardly of the obturator but inwardly of the trocar cannula;  
       FIG. 33  is a side elevation view of a blunt-nose obturator having windows to facilitate the return of the inverting sheath to an interior channel of the obturator;  
       FIG. 34  is a cross section view taken along lines  34 - 34  of  FIG. 33 ;  
       FIG. 35  is a side elevation view similar to  FIG. 33  and showing an obturator tip with converging planes;  
       FIG. 36  is a front elevation view taken along lines  35 - 35  of  FIG. 34 ;  
       FIG. 37  is an axial cross section view of an obturator similar to that of  FIG. 34  and including a biasing means for returning the inverting sheath to its initial position;  
       FIG. 38  is an axial cross section view similar to  FIG. 37  and illustrating the biasing means stretched to a final position of the inverting sheath;  
       FIG. 39  illustrates a fabric adapted for use as a traction tread or sheath, the fabric being illustrated in a normal state;  
       FIG. 40  is a side elevation view of the mesh of  FIG. 39  axially stretched;  
       FIG. 41  is a side elevation view of the mesh of  FIG. 39  radially stretched;  
       FIG. 42  is an end view of the traction sheath formed of the mesh of  FIG. 39 ;  
       FIG. 43  is an end view similar to  FIG. 41  of the inverting sheath forming pleats to provide texture for traction;  
       FIG. 44  is a side elevation view of a further embodiment of the obturator including a blunt tip with a conical point for microscopic puncture;  
       FIG. 45  is an end view taken along lines  45 - 45  of  FIG. 44 ;  
       FIG. 46  is a perspective view of an application adapted for use in placing the trocar system of the present invention;  
       FIG. 47  is a schematic axial cross section view of a further embodiment including gears with circumferential teeth;  
       FIG. 48  is an end view of the embodiment illustrated in  FIG. 47 ;  
       FIG. 49  is a schematic axial cross section view of a further embodiment including a single oscillating gear; and  
       FIG. 50  is an end view of the embodiment of  FIG. 49 . 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS AND BEST MODE OF THE INVENTION  
      A trocar system of the present invention is illustrated generally in  FIG. 1  and designated by the reference numeral  10 . The system  10  includes a trocar cannula  12  having a seal housing  14 , and an obturator  16  with a shaft  18  and handle  21 , and including a traction mechanism  23  of particular interest to the present invention. The obturator  16  is used in placing the cannula  12  across a body wall such as an abdominal wall  25 , associated with a patient  27 . In the case of the abdomen, the wall  25  defines an abdominal cavity  29  which includes many organs such as that designated by the reference numeral  30 .  
      In less evasive laparoscopic procedures, multiple cannulas  32  and  34  are used to provide access across the abdominal wall  25  to facilitate surgical procedures within the abdominal cavity  29 . By way of example, the removal of a gallbladder is typically accomplished with such a laparoscopic procedure. Initially, cannulas  12 ,  32  and  34  are placed across the abdominal wall  25 , each providing a working channel through which various instruments can be inserted and surgically manipulated. For example, the cannula  32  is shown with a grasper  36  which can be inserted through the cannula to grasp the organs  30  or other tissue within the abdominal cavity  29 . A fiber-optic scope  38  is illustrated in  FIG. 1  operatively disposed through the cannula  34  and across the abdominal wall  25  to provide visualization within the abdominal cavity  29 .  
      As further background to the trocar system  10  of the present invention,  FIGS. 2-5  are provided and to illustrate the deficiencies of trocars and obturators of the prior art.  
      One trocar of the prior art is illustrated in  FIG. 2  and is designated by the reference numeral  41 . This trocar includes a cannula  43  and blunt obturator  45 . In the placement of this device, an incision  47  is cut entirely through the abdominal wall  25  using a scalpel  50 . All of the deficiencies previously discussed with respect to cutting rather than parting the abdominal wall  25  impact this procedure. After the incision  47  is cut, the blunt obturator  45  is moved through the incision to place the cannula  43  across the wall  45 . Due to the delicate cutting required by this procedure, placement of this trocar  41  may take as long as 10 minutes. In a procedure requiring the placement of four trocars, this time intensive procedure would require as much as 40 minutes, for example.  
      In comparison, placement of a self-cutting obturator may require only one minute of time. In a procedure requiring the placement of four trocars, this part of the procedure may require only four minutes of time as opposed to the 40 minutes of time required for the precut procedure of  FIG. 2 .  
      A self-cutting trocar system  52  of the prior art is illustrated in  FIG. 3 . This system  52  includes a cannula  54  and an obturator  56  having a pair of opposing wings  58 . These wings  58  ate provided with sharpened outer edges so that they tend to cut a path through the abdominal wall  25 . Again, the disadvantage of cutting an incision through the abdominal wall  25  also impacts this embodiment.  
      Perhaps the most widely used embodiment of a trocar is that illustrated in  FIGS. 4 and 5 . In this case, a trocar  61  includes a cannula  63  and obturator  65  having a sharpened point  67 . A safety shield  70  associated with the obturator  65  is biased to move over the point  67  and to protect the interior organs  30  upon penetration of the abdominal wall  25 . In the process associated with this instrument, the trocar  61  is forced through the abdominal wall  25  creating a significant distal force on the wall  25 . This distal force provides the wall  25  with a concave shape, commonly refereed to as tenting, and tends to bring the point  67  into close proximity to the interior organs  30 .  
      As with the prior art embodiment of  FIG. 3 , the point  67  precedes the remainder of the trocar  61  as it cuts the tissue of the wall  25 . Therefore, of the deficiencies previously discussed with reference to cutting are applicable to this prior art embodiment. Furthermore, the significant force required fox penetration, a force typically as high as ten pounds, coupled with close proximity of the concave wall  25  to the organs  30 , tends to provide little time for the safety shield  70  to cover the tip  67 . As a consequence, damage to the interior organs  30  has been severe notwithstanding the presence of the safety shield  70 .  
      The high forces required for penetration are particularly applicable to those trocar systems which require both penetration forces as well as cutting forces.  
      In all of these embodiments of the prior art, it will be noted that cutting of the abdominal wall is required. Furthermore, all forces associated with movement of the trocars  41 ,  52  and  61  though the abdominal wall  25  produce a distal force as great as ten pounds which tends to move the abdominal wall  25  into a concave shape and into close proximity with the interior organs  30 .  
      The advantages of the trocar system  10  of the present invention will be readily apparent with reference to the obturator  16  of  FIG. 6  and a comparison with the prior art devices illustrated in  FIGS. 2-5 . As previously discussed, this obturator  16  includes the shaft  18 , handle  21  and traction mechanism  23 . In this case, the traction mechanism  23  may include a fabric  72  having the configuration of a tube with a first end  74  and a second end  76 . In this context, the word “fabric” refers to any flexible sheet material. The shaft  18  can be solid, but in a preferred embodiment it is at least partially hollow to receive the first end  74  of the fabric  72  within the shaft  18 . The shaft  18  extends to a distal tip  78  having a wall  81  that defines an internal channel  83  and an axial hole  85 . This wall  81  is defined by a leading surface  87 .  
      The tubular fabric  72  is initially disposed with its first end  74  positioned in the interior channel  83 . The fabric  72  extends distally outwardly through the hole  85  where it inverts and extends proximally along the leading surface  87  and the outer surface  90  of the shaft  18 . At the second end  76 , the tubular mesh is preferably attached to a finger engagement means, such as a projection, tab, flange or ring  92 .  
      In operation, the handle  21  of the obturator  16  is placed in the palm of the user&#39;s hand and his/her fingers are extended to engage the ring  92 . In a common and familiar motion, the hand of the user is closed drawing the fingers towards the palm of the hand. This moves the ring  92  toward the handle  21  and draws the tubular fabric  72  distally through the hole  85  and proximally along the outer surface  90  of the shaft  18 . As the ring  92  moves proximally upwardly in  FIG. 6 , the first end  74  of the fabric  72  is pulled toward the distal tip  78  where the fabric  72  exits the hole  85  and inverts to move along the outer surface  90 . With the fabric  72  disposed between the shaft  18  and the abdominal wall  25 , it tends to grip the abdominal wall  25 , and move the wall  25  proximally along the shaft  18 . As the wall  25  moves upwardly in  FIG. 6  along the shaft  18 , it tends to part at the leading edge  87  along a line of weakness designated generally by the reference numeral  94 . It is of particular importance to note that the wall  25  is parted rather than cut in order to achieve the advantages previously discussed. In this particular, embodiment, there is no structure which works to cut the abdominal wall  25  or otherwise force the obturator  16  along a predetermined path. Rather, the obturator  16  finds its own path along the line of weakness  94 .  
      Notwithstanding this significant aspect of the present invention, perhaps the greatest advantage is achieved with a net zero or even proximal force on the wall  25 . As previously noted, the prior art produced only a distally directed force in creating an incision while moving an obturator through the abdominal wall. This tended to move the abdominal wall toward a concave shape and into proximity with the internal organs. With the present embodiment, the handle  21  can be held stationary with a distally directed force, shown by an arrow  96 , while a counter proximal force of equal or greater magnitude is applied to the ring  92 , as shown by the arrows  98 .  
      Since these forces, shown by the arrows  92  and  98 , are applied in different directions, they tend to offset each other so that the net distal force applied to the abdominal wall  25  can actually be negative. Note for example, that if the handle  21  is maintained stationary, and the ring  92  is moved upwardly, the net force on the abdominal wall  25  is a proximal force directed upwardly in  FIG. 6 . As a result, the abdominal wall  25  can be moved toward a convex shape and a spaced relationship with the interior organs  30 .  
      It will be appreciated from the foregoing discussion, that the counter forces which are of particular advantage to the present invention can be produced from a variety of structures. More specifically, the tubular fabric  72  discussed with reference to  FIG. 6  can be any material capable of being pulled along the outer surface  90  of the shaft  18 . This material could be organic or inorganic and will generally be elongate so that it tan be pulled with some magnitude of force in the axial, proximal direction. For example, the tubular fabric  72  of  FIG. 6 , although preferred for that embodiment, could be replaced with just a single traction tread  101  as illustrated in  FIG. 7 . With this traction tread  101  disposed between the shaft  18  and the abdominal wall  25 , the traction tread  101  will engage the tissue of the abdominal wall  25  and pull it proximally relative to the shaft  18 .  
      Forces will be more balanced if at least two traction treads, such as the tread  101  and a second tread  103 , were diametrically opposed as illustrated in  FIGS. 9 and 10 . With this configuration, the abdominal wall  25  ( FIG. 1 ) is engaged on both sides of the shaft  18  and pulled proximally relative to the shaft  18 .  
      Other embodiments of the invention might include three traction treads, such as the treads  101  and  103  and a third tread  105  equally spaced around the circumference of the shaft  18 . Such an embodiment is illustrated in  FIGS. 11 and 12 .  
      While independent and discrete traction treads, such as the treads  101 ,  103  and  105 , will function to produce the discrete counter forces, a single traction tread that is radially continuous, as illustrated in  FIGS. 13-15 , may be preferred as it provides complete isolation of the shaft  18  from the abdominal wall  25  ( FIG. 1 ). Where the shaft  18  of the obturator  16  is cylindrical and the distal tip  78  is conical or convex as it as illustrated in  FIG. 13 , this tubular configuration for the traction tread  107  is particularly desirable. With this configuration, the traction tread  107  passes through the axial hole  85  where it inverts and travels radially as shown by arrows  110  in  FIG. 15 . From this point, the traction tread  107  travels proximally along the surface  90  of the shaft  18 , upwardly in  FIG. 14 .  
      In a further embodiment of the invention, the distal tip  78  of the obturator  16  is formed as a pair of planar surfaces  112  and  114  which converts distally in the nature of a flathead screwdriver. This configuration lends itself to the opposing pair of tractor treads  101  and  103  previously illustrated in  FIGS. 9 and 10 . With this construction, the traction treads  101  and  103  separate generally at an exit slot  116  best shown in  FIG. 18 . In this view the opposing forces are shown by the arrows  118  and  121  which produce the tissue parting results of particular advantage to the present invention.  
      With reference to  FIGS. 19, 20  and  21 , it can be seen that a similar embodiment including the converging surfaces  112  and  114  can be accommodated with traction treads  101  and  103  which are axially continuous. Thus, each of these treads  101  and  103  forms a continuous band  123  and  125  respectively. The two bands  123 ,  125  counter rotate through the slot  116 , and extend proximally along the surface  90 , returning to the interior channel  83  through opposing windows  127  and  130  in the wall  81  of the obturator.  
      With respect to the embodiment of  FIG. 6 , the method of operation will now be discussed with reference to  FIGS. 22-78 . In these views, the abdominal wall  25  is further defined by a fascia  141 , muscle tissue  143 , and a peritoneum  145 . In this case, the shaft  18  and fabric  72  of the obturator  16  can be inserted through the seal housing  14  and into the cannula  12 . A distal end  147  of the cannula  12  is disposed through the ring  92  and into the associated tubular fabric  72 . In operation, the trocar system  10  functions by pulling the ring  92  proximally along an outer surface  149  of the cannula  12 , upwardly in  FIG. 22 .  
      In an initial step of the process, a cut  152  can be made in the skin or fascia  141 . This cut  152  is preferably made to gain access to the muscle tissue  143  which is more easily parted. The cut  152  also marks the desired location for insertion of the trocar system  10 . As the ring  92  is drawn upwardly along the cannula  12 , the tubular fabric  72  exits the distal hole  85 , inverts and follows the ring  92  upwardly along the outer surface  149 . At the leading surface  187 , the inverting fabric  72  produces opposing radial forces shown by arrows  152  and  154 . With these opposing forces, the tissue  143  is parted along the line of weakness  94  ( FIG. 6 ) as the trocar system  10  is moved relatively into the abdominal wall  25 . It will be noted that the arrows  152  and  154  are merely representative of all of the radial forces which emanate from the hole  85  as shown by the arrows  110  in  FIG. 15 .  
      With reference to  FIG. 23 , it can be seen that the ring  92  and inverted tubular fabric  72  are preferably drawn proximally by the arrows  98  while the cannula  12  and obturator  16  are held stationary as shown by a pair of arrows  156 . This produces the counter forces previously described and elevates the abdominal wall  25  as it is pulled proximally upwardly along the cannula  12  by the fabric  72 .  
      Full penetration of the abdominal wall  25  including the peritoneum  145  is illustrated in  FIG. 124 . It is interesting to suspend further description at this point and note that on the distal side of the abdominal wall  25 , the trocar system  10  presents no sharp objects that might be detrimental to the interior organs  30 . There is no scalpel ( FIG. 2 ), no sharp wings  56  ( FIG. 3 ), and no sharp cutting point  67  ( FIG. 5 ) characteristic of this prior art. Furthermore, the space between the abdominal wall  25  and the interior organs  30  is actually increased by the net proximal force associated with operation of the trocar system  10 . This space can be even further increased as illustrated in  FIG. 25  by merely pulling on the trocar system  10  to further elevate the convex abdominal wall  25  into a more conical configuration.  
      Once the trocar system  10  has fully penetrated the abdominal wall  25 , the ring  92  can be drawn further upwardly along the cannula  12  into contact with the seal housing  14 . In a preferred embodiment, this disposition of the ring  92  will cause the first end  74  of the tubular fabric  72  to exit the axial hole  85  of the shaft  18  ( FIG. 25 ). At this point, the obturator  16  can be removed, leaving the seal housing  14 , associated cannula  12  and tubular fabric  72 . With the obturator  16  removed, the interior working channel of the cannula  12  is vacated to facilitate access with surgical instruments, such as the endoscope  38  and grasper  36  illustrated in  FIG. 1 .  
      Even during this stage of the process, the trocar system  10  of the present invention offers significant advantages. Noteworthy in this embodiment is the fact that the tubular fabric  72  remains between the cannula  12  and the abdominal wall  25  even after the obturator  16  is removed. In this position, the high traction characteristics which facilitated penetration of the abdominal wall  25  by the trocar system  10 , remains to ensure that the cannula  12  stays in place during the insertion and removal of surgical instruments. The structure that aided in penetration of the abdominal wall  25  now aids in maintaining the cannula  12  in its preferred operative disposition.  
      When the surgical operation is complete, the cannula  12  and associated valve housing  14  ( FIG. 26 ) can be removed, from the ring  92  and attached tubular, fabric  72 . This removal of the cannula  12  maybe inhibited in an embodiment wherein the tubular fabric  72  is automatically biased to a reduced profile. This bias tends to exert radial forces on the cannula increasing the amount of friction which must be overcome to separate the cannula  12  from the tubular fabric  72 . In such an embodiment, it has been found that application of an axial force on the ring  92  and attached tubular fabric  72 , will tend to radially expand the fabric  72 . In  FIG. 26 , this axial force is represented by an arrow  160 . With this radial expansion of the fabric  72 , the cannula  12  and associated salve housing  14  can be removed from the tubular fabric  72 .  
      Without the large cannula  12  radially stretching the fabric  72 , the tubular configuration will automatically be drawn down to a reduced diameter as illustrated in  FIG. 27 . This lower profile greatly facilitates removal of the tubular fabric  72  as illustrated in  FIG. 28  by an arrow  161 . It will be noted that once the tubular fabric  72  is withdrawn, the abdominal wall  25  is left with the parted line of weakness  94  initially discussed with reference to  FIG. 6 .  
      An additional embodiment of the invention is illustrated in the progressive views of  FIGS. 29-32 , wherein elements of structure similar to those previously discussed are designated with the same reference numeral followed by the loner case letter “a.” Thus the trocar system  10   a  is shown with the cannula  12   a  and associated seal housing  14   a . The obturator  16   a  includes the shaft  18   a  and handle  21   a , as well as the axial hole  85   a . The tubular fabric is designated with a reference numeral  72   a . Note that in this embodiment the tubular fabric  72   a  also extends through the valve housing  14   a  to the ring  92   a  which is disposed proximally of the valve housing  14   a.    
      This embodiment differs from that previously disclosed in that the obturator  16   a  and tubular fabric  72   a  are disposed entirely within the working channel of the cannula  12   a . Thus, the obturator  16   a  with fabric  72   a  is inserted into the cannula  12   a  in the initial step of operation. It will be noted that with this construction, the fabric  72   a  is exposed to the abdominal wall  25  ( FIG. 1 ) only in a distal region  163  where the obturator shaft  19   a  is exposed distally of the end  132   a  of the cannula  12   a . Since this region produces the parting forces represented by the arrows  152  and  154  in  FIG. 22 , as well as the proximal counter forces, represented by the arrows  98  in  FIG. 6 , this embodiment provides many of the advantages previously discussed.  
      In operation, the obturator  16   a  with tubular fabric  72   a  is disposed in the cannula  12   a . The leading edge  87   a  is brought into contact with the body wall  25   a  and the ring  92   a  is drawn proximally toward the handle  21   a  as illustrated in  FIG. 30 . As the tubular mesh emanates from the axial hole  85   a  it inverts in the manner previously discussed pulling the abdominal wall  25   a  upwardly onto the cannula  12   a . The ring  92   a  is drawn proximally into an abutting relationship with the handle  21   a  as illustrated in  FIG. 31 . At this point, the cannula  12   a  should be fully inserted through the abdominal wall  25   a . Following this step in the surgical procedure, the obturator  16   a  as well as the tubular fabric  72   a  can be entirely withdrawn leaving the cannula  12   a  operatively disposed across the abdominal wall  25   a  as illustrated in  FIG. 32 .  
      One of the significant advantages associated with this embodiment is that the obturator  16   a  and tubular fabric  72   a  can be repeatedly used in the placement of multiple cannulas, such as the cannula  12   a . Thus, a first cannula can be placed through the abdominal wall using the obturator  16   a . Upon removal of the obturator  16   a , the first cannula can be left in place as illustrated in  FIG. 32 . Then the obturator  16   a  can be inserted into a second cannula to facilitate its placement across the abdominal wall. The same obturator  16   a  can then be removed to facilitate placement of additional cannulas.  
      A further embodiment of the invention is illustrated in  FIGS. 33-35  where elements of structure similar to those previously discussed are designated with the same reference numeral followed by the lower case letter “b.” This embodiment is similar to that discussed with reference to  FIG. 29  in that the obturator  16   b  and tubular fabric  72   b  are formed as a subassembly which is inserted into the cannula  12   b . Thus, the tubular fabric  72   b  is only exposed in the distal region  163   b  distally of the distal end  132   b  of the cannula  12   b.    
      The embodiment of  FIG. 33  differs from that of  FIG. 29  in that the tubular, fabric  72   b  moving proximally is not disposed between the obturator shaft  18   b  and the cannula  12   b . Rather, the proximally moving tubular fabric  72   a  is disposed exteriorly of the shaft  18   b  only in the distal region  163   b . At the proximal end of this region  163   b , in proximity to the distal end  132   b  of the cannula  12   b , the proximal moving tubular fabric  72   b  is directed through the windows  127   b  and  130   b  back into the interior channel  83   b  of the shaft  18   b.    
      Within the channel  83   b , the second end  76   b  of the tubular fabric  72   b  is attached to the ring  92   b . This calls for a special construction of the shaft  18   b  and ring  92   b  which is best described with reference to the radial cross section view of  FIG. 34 . In order to attach the second end  76   b  of the tubular fabric  72   b  (which is disposed interiorly of the shaft  18   b ) to the ring  92   b  (which is disposed exteriorly of the shaft  82   b ), some structure is required to extend through the wall  81   b  of the shaft  18   b . Initially, the shaft  18   b  can be formed with axial slots  165  which extend along the shaft  18   b  beneath the ring  92   b . These axial slots  165  are preferably equally spaced around the circumference of the shaft  18   b . Spokes  167  integrally molded with the ring  92   b , can be positioned in the slots  165  of the shaft  18   b  to extend from regions exterior of the shaft  18   b  to regions interior of the shaft  18   b . Within the channel  83   b , the second end  76   b  of the tubular mesh can be attached to the spokes  167 .  
      A similar embodiment of the invention is illustrated in  FIG. 5  where elements of structure similar to those previously discussed are designated by the same reference numerals followed by the lower case letter “c.” In this case, the obturator shaft  18   c  is formed at its distal end with a structure similar to that illustrated in  FIG. 16 . Thus, the shaft  18   c  is formed with the converging planar surfaces  112   c  and  114   c  and the separate traction treads  101   c  and  103   c , best illustrated in  FIG. 36 . As previously discussed, this embodiment requires both of the windows  127   c  and  133   c , as well as the slot  116   c . This embodiment of the trocar system  10   c  offers a further advantage that the obturator  16   c  can be used repeatedly with multiple cannulas  12   c.    
      For those embodiments which offer this choice of repeated use, such as the embodiments of  FIGS. 29, 33  and  36 , it may be desirable to provide some means for recycling the obturator  16  as illustrated in  FIG. 37 . In this case, a tension spring  170  is fixed at one end to the handle  21   c  and at the other end to the first end  74   c  of the tubular fabric  72   c . In operation, the ring  92   c  is drawn proximally toward the handle  21   c  along with the second end  76   c  of the tubular fabric  72   c . This causes the first end  74   c  of the tubular fabric  72   c  to move distally stretching the spring  170 . The spring  170  is stretched even further ( FIG. 3 ) as the ring  92   c  is drawn proximally and the traction treads  101   c  and  103   c  pass outwardly through the axial slot  116   c  and inwardly through the windows  127   c  and  130   c , respectively. When this operation is completed and the associated cannula  12   c  is placed across the abdominal wall  25   c , the obturator  16   c  can be withdrawn and the ring  92   c  released from its proximal-most position ( FIG. 38 ). At this point, the bias of the spring  170  will pull the first ends  74   c  of the traction treads  101   c ,  103   c  proximally. As the obturator  16   c  is reset, the treads  101   c ,  103   c  will pass outwardly through the windows  127   c ,  130   c , respectively, and inwardly through the axial slot  116   c . This will enable the spring  170  to return to its normal, non-stretched state with the ring  92   c  disposed in its distal most position.  
      It can be appreciated that the spring  170  could be replaced with any biasing means which mechanically, electrically or elastomericallyo, for example, would bias the first end  74   c  in the proximal direction.  
      With the foregoing description of these preferred embodiments, it can be appreciated that the structure forming the tubular fabric  72  as well as the various traction treads  101 ,  103 ,  105  and  107 , is of particular importance to the present invention. This structure is preferably formed as a sheet material and is flexible and elongate with at least one tractive surface. These characteristics will be appreciated particularly in those embodiments involving the traction treads  101  and  103  where the width of the treads remains generally constant. In these cases, the tread is able to maintain its width as it exits the distal slot  116  and enters the windows  127  and  130 .  
      For those embodiments involving the distal exit hole  85 , it may be further desirable if the structure of the fabric is capable of radially expanding and contracting. Particularly if the mesh is biased to the contracted low-profile state, it will occupy less space within the interior channel  83  and more easily feed through the exit hole  85 . A bias to the contracted state will also facilitate removal of the fabric  72  as illustrated in  FIG. 28 .  
      As noted, the fabric  72  preferably has a sheet configuration and can be either woven or non-woven. It can be formed with filaments, which in the preferred embodiment of  FIG. 39 , are divided into filament groups  170  and  172  that extend in transverse directions. Thus the filaments in the group  170  may extend, in a normal state, perpendicular to the filaments in the group  172 , as illustrated in  FIG. 39 .  
      In order to facilitate the traction characteristics of the material  168 , the filament groups  170  and  172  can be woven to form points of intersection  174  where the filaments cross and spaces or interstices  176  between the filaments. At the points of intersection, the fabric  72  will have a thickness equal to the sum of the diameters of a single filament in the group  170  and a single filament in the group  172 . Between the points of intersection, the filaments in the groups  170  and  172  will provide the fabric  72  with only a single thickness. In the interstices  176  between the filaments of the groups  170  and  172 , the material  168  will have zero thickness. Thus, the woven configuration of even this simple embodiment will provide the fabric  72  with three different thicknesses greatly facilitating the traction between the material  168  and the tissue associated with the abdominal wall  25  ( FIG. 1 ).  
      Even those significant traction characteristics can be dramatically increased with simple variations in the weave parameters. Consider for example the effect of making the various filament groups  170 ,  172  with different diameters. With an appropriate weave, this could add two additional levels of thickness to the fabric  72 . Thus it is contemplated that any of the weaves known in the textile industry could provide multiple levels of thickness having dramatic effects on the traction of the fabric  72  relative to the tissue of the abdominal wall  25  ( FIG. 1 ).  
      It should also be considered that any one of the filaments in the groups  170  and  172  can be formed from a different material. Solid, non-resilient materials, such as monofilament, will tend to maintain their shape providing more of a mechanical traction to the tissue. The filaments could also be formed from fibrous materials, such as cotton, in which case traction would be further enhanced by capillary action. The filaments of the groups  170 ,  172  could also be individually varied in their diameters or thicknesses, or provided with a more tractive surface, shape or coating.  
      In a preferred embodiment, the filaments forming the group  170  include monofilaments which are alternated with cotton filaments. The same alternation of filament materials is applied to the filaments of the group  172 . With even a simple weave of these filament groups  170  and  172 , significant variations in thickness occur due to the fixed diameter of the monofilaments and the variable diameter of the cotton filaments. The resulting material  168  provides many different thicknesses for high mechanical traction and additionally provides the capillary action associated with fibrous cotton material.  
      Thermoplastic materials can also be used for the filaments in the groups  170  and  172 . These materials will permit the fabric  72  to be biased to a compacted state as illustrated in  FIG. 40  and stretched to an expanded state as illustrated in  FIG. 41 . This thermoplastic bias facilitates movement of the tubular fabric  72  between a low profile state interiorly of the shaft  18   b , and an expanded high profile state exteriorly of the shaft  18   b . With a bias to the low profile state, the tubular fabric  72  will automatically contract to achieve the advantages previously discussed.  
      The fabric  72  can also be woven in a manner that the filaments of the group  170  are fixed to the filaments of the group  172  at each point of intersection  174 . This feature will tend to make the fabric  168  more rigid so that it does not tend to close down on the surface of the cannula  12  or shaft  18  as it is drawn proximally. The resulting fabric  72  will also have less of a tendency to expand or contract. This may tend to produce pleats in the fabric  72  particularly where it emanates from the axial hole  85   b . With reference to  FIG. 42 , it can be seen that these pleats  178  can provide the further advantage of texture variations at the critical leading surface  87  of the obturator  16 . This additional texture can even further enhance the traction with the tissue where the important parting of the tissue is taking place.  
      Alternatively, the filaments forming the group  170  and  172  can remain disconnected at their points of intersection  74 . This will enable the filaments to move over each other enhancing their ability to expand and contract. The characteristic of this weave is best illustrated in  FIG. 43  where the fabric  168  tends to maintain its cylindrical configuration as it passes through the axial hole  85  and moves from the low profile state to the high profile state.  
      In a particular embodiment of the invention it may be desirable to control the stretchability of the fabric  168  in different directions. For example, it may be desirable to facilitate radial expansion while inhibiting axial expansion. The radial expansion might be desirable as it facilitates the transition of the tubular fabric  72  from the low profile state at the exit hole  85   b , to the high profile state exteriorly of the cannula  12  or shaft  18 . At the same time, it might be desirable to inhibit expansion or contraction in the axial direction. Alternatives for providing different stretch characteristics in different directions are well known in the textile industry and include formation of the fabric  72  with filaments of different material and shape as well as orientation of the filaments relative to the cut of the fabric  168 .  
      A further embodiment of the invention is illustrated in  FIG. 44  where elements of structure similar to those previously discussed are designated with the same reference numeral followed by the lower case letter “d.” In the side elevation view of  FIG. 44 , the obturator  16   d  is illustrated with its wall  81   b  extending along an axis  181  to form a blunt tip  183  and the exit hole  85   d . A needle  185  having a sharp conical tip  187  is supported within the interior channel  83   d  to extend slightly through the axial hole  85   d . In this embodiment, the tubular mesh  82   d  is disposed around the needle  185  and exits through the axial hole  85   d  and proximally along the wall  81   d  in the manner previously discussed. The needle  185  can be fixed to the obturator  16   b , or can be moveable distally, either manually or automatically, to facilitate penetration of the wall  25 .  
      With this construction, the needle  185  can provide a microscopic puncture which precedes the fabric  72   d  as it exits from the hole  85   d . This microscopic puncture can provide the initial cut  152  in the fascia  141  and/or facilitate puncture of the peritoneum  145  ( FIG. 22 ). Even in this embodiment it is desirable that the paring forces represented by the arrows  152  and  154  of  FIG. 22  predominate over any cutting associated with the conical tip  187 . This will ensure that the obturator  16  progresses along the line of weakness  94  to achieve the advantages previously discussed with reference to  FIG. 6 .  
      An insertion apparatus  201  adapted for use with the trocar system  10  of the present invention is illustrated in  FIG. 46 . This particular embodiment of the trocar system  10  includes the obturator handle  21 , valve housing  14 , cannula  12  and ring  92  coupled to the tubular fabric  72 . The insertion apparatus  201  includes a frame  203  fixed to a longitudinal tray  205  that extends along an axis  206  to a distal radial wall  207 . The frame  203  includes a palm handle  210  and finger handle  212  which operate a ratchet mechanism  214  to move a plunger  216  and a distal engagement pad along the tray  205 .  
      In operation, the trocar system  10  is placed within the tray  205  and aligned axially with its cannula  12  extending through a hole  221  in the distal wall  207 . Importantly, the ring  92  is disposed on the proximal side of the wall  207 .  
      Mechanical, electrical, or hydraulic operation of the handles  210 ,  212  moves the plunger  218  axially distally bringing the engagement pad  217  into contact with the handle  21  of the trocar system  10 . Further operation of the handles  210  and  212  operates the ratchet assembly  214  to move the cannula  12  distally within the tray  205  of the insertion apparatus  201 . With distal movement of the ring  92  inhibited by the wall  207 , the ring  92  moves proximally relative to the advancing cannula  12 . This deploys the tubular fabric  72  and causes it to move proximally relative to the outer surface of the cannula  12 .  
      Use of this insertion apparatus  201  can significantly aid in placement of the trocar system  10 . It not only provides some mechanical advantage to the process but is also operable by a single hand of the user.  
      In a further embodiment of the invention illustrated in  FIG. 47 , elements of structure similar to those previously discussed are designated by the same reference numeral followed by the lower case letter “D.” Thus, this embodiment includes the obturator  16   b  with shaft  18   b  having the distal tip  78   b . In this embodiment, a pair of gears  230  and  234  are rotatable on the shaft  18   b  and disposed radially with respect to each other. Teeth  234  and  236  on the circumference of the gears  230  and  232  extend beyond the distal tip  78   b  and form the leading surface  87   b  of the obturator  16   b . The teeth  234  and  236  mesh between the gears  230  and  232  so that these gears turn in opposing directions generating the parting forces illustrated by the arrows  152   b  and  154   b . A pilot gear  138  can be used to rotate one of the gears  130 ,  132  which in turn rotates the opposing gear  232  or  230  respectively. The pilot gear  238  can be rotated by any suitable mechanism, such as a belt  241  receiving an applied force from the proximal end of the obturator  16   b . In this case it can be seen that the traction treads mentioned with respect to previous embodiments take the form of the gear teeth  234  and  236  which are axially continuous and produce the parting forces at the leading surface  187   b . An end view of this embodiment is illustrated in  FIG. 48 . A further embodiment of the invention is illustrated in the axial cross section view of  FIG. 49  and the associated end view of  FIG. 50 , where elements of structure similar to those previously disclosed are designated by the same reference numeral followed by the lower case letter “E.” Thus, the obturator  16   e  includes a single gear  243  exposed at the distal tip  78   e . In this case, the idle ear  238   e  is rotatable by the belt  241   e  alternately clockwise and counter-clockwise. This oscillating movement is transferred to the gear  230   e  causing its teeth  234   e  to move back and forth at the leading surface  87   e . This oscillating movement is illustrated by an arrow  245  in  FIGS. 49 and 50 .  
      Many alterations aid modifications can be made to the foregoing preferred embodiments without departing from the spirit and scope of the invention. Therefore it must be understood that the illustrated embodiments have been set forth only by way of example, and should not be taken as limiting the invention. For example, notwithstanding the fact that the claims set forth below recite certain elements and combinations, it must be expressly understood that the invention includes other combinations of fewer, more or different elements, which are not disclosed above even when not initially claimed in such combinations.  
      In addition, the words used in this specification to describe the invention and its various embodiments ate to be understood not only in the sense of their commonly defined meanings but also in the sense of any special definitions used in this specification, which may extend beyond the scope of the commonly defined meanings. Thus if an element can be understood in the context of this specification as including more than one meaning, than its use in the claims must be understood as being generic to all possible meanings supported by the specification and by the word itself.  
      The definitions of the words or elements of the following claims are, therefore, defined in the specification to include not only the combination of the elements which are literally set forth, but all equivalent structure, material or method steps for performing substantially the same function, in substantially the same way, to obtain substantially the same way to obtain substantially the same result in this sense it is therefore contemplated that an equivalent substitution of two or more elements may be made for any one of the elements in the claims below or that a single element may be substituted for two or more elements in a claim. Insubstantial changes from the claimed subject matter, now known or later devised, are expressly contemplated as being equivalently within the scope of the claims. Therefore, obvious substitutions now or later known to one with ordinary skill in the art are deemed to be within the scope of the defined elements.  
      The claims are thus to be understood to include what is specifically illustrated and described above, what is conceptually equivalent, what can be obviously substituted, and also what essentially incorporates the idea of the invention.  
      Many alterations arid modifications can be made to the foregoing preferred embodiments without departing from the spirit and scope of the invention. Therefore it must be understood that the illustrated embodiments have been set forth only by way of example, and should not be taken as limiting the invention. For example, notwithstanding the fact that the claims set forth below recite certain elements and combinations, it must be expressly understood that the invention includes other.