Abstract:
A trocar sleeve has a hollow shaft having a distal end and a proximal end, the shaft having a rectilinear shaft axis, an external thread rising from an outer surface of the shaft, wherein a first external thread having a shape of a helix has a height, measured from the outer surface up to a vertex of the helix, the height of the helix, seen along the rectilinear shaft axis from distal to proximal increases, and wherein a pitch of the helix, seen along the rectilinear shaft axis from distal to proximal decreases.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to a trocar sleeve with a hollow shaft which has a distal end and a proximal end and an approximately rectilinear shaft axis, with an external thread rising from the outer face of the shaft. 
       BACKGROUND OF THE INVENTION 
       [0002]    A trocar sleeve of this kind is known from EP 0 484 725 A. 
         [0003]    Trocar sleeves are used in minimally invasive procedures to gain access to an internal cavity of the body. In laparoscopy, this is the abdominal cavity. For this purpose, the trocar sleeve has a hollow shaft which, when the trocar sleeve is applied, is placed over an incision in the abdominal wall and pushed through the latter. Thereafter, the distal end of the shaft protrudes into the abdominal cavity, while the proximal end protrudes from the upper face of the abdominal wall 
         [0004]    In many embodiments, the trocar sleeve is applied by pushing a trocar mandrel into the hollow shaft, said trocar mandrel having a distal tip which extends beyond the distal end of the trocar sleeve. This combination of trocar sleeve and trocar mandrel, i.e. the actual trocar, is pushed through the abdominal wall. Thereafter, the trocar mandrel is withdrawn, such that suitable instruments can then be inserted through the hollow shaft into the body cavity. 
         [0005]    In many trocar sleeves, a helically extending external thread is present on and rises from the outer face of the hollow shaft. The trocar sleeve can be screwed in or out through the tissue via this thread. 
         [0006]    Particularly in laparoscopy procedures, it is desirable to inflate the internal cavity of the body, i.e. the abdominal cavity, with an insufflation gas in order to provide a better view of the interior. For this purpose, a housing provided with a seal, and with an attachment for delivery of an insufflation gas, is mounted in most cases on the proximal end of the shaft of the trocar sleeve. In many designs, further attachments can be provided on the trocar housing, for example in order to deliver and remove irrigation liquids. In practical use, corresponding hose lines are then attached, as a result of which the trocar sleeve becomes rather top-heavy. This poses the risk of the trocar sleeve changing its position during use, for example by moving in the proximal direction or tilting. It would be fatal if the trocar sleeve were to accidentally slide out of the body during an endoscopy procedure. 
         [0007]    In some embodiments, the hollow shaft is made from a flexible material, mostly a plastic material. The clear internal diameter of the hollow shaft defines the maximum diameter of an instrument that can be guided through the trocar sleeve. In many surgical techniques, it is necessary to insert instruments that are curved or are bent sideways. In the case of rigid trocar sleeves, for example those made of steel, such instruments cannot be guided through, or they can be guided through only with deformation. In these cases, flexible trocar sleeves are used. The tubular body of the hollow shaft is made from an elastic polymer that is able to adapt to the bending of the surgical instruments that are passed through. When bent instruments are guided through a trocar sleeve, there is a danger of the latter being shifted. 
         [0008]    Moreover, the plastic materials that are used generally have lower coefficients of friction than the materials of rigid trocar sleeves, such that there is additionally the danger of a fitted trocar sleeve shifting. 
         [0009]    It is an object of the present invention is to develop a trocar sleeve that can be inserted with minimal trauma into a cavity of the body and that is secured at least against withdrawal from the body. 
       SUMMARY OF THE INVENTION 
       [0010]    According to the invention, the object is achieved by a trocar sleeve, comprising a hollow shaft having a distal end and a proximal end, said shaft having a rectilinear shaft axis, an external thread rising from an outer surface of said shaft, wherein a first external thread having a shape of a helix has a height, measured from said outer surface up to a vertex of said helix, said height of said helix, seen along said rectilinear shaft axis from distal to proximal increases, and wherein a pitch of said helix, seen along said rectilinear shaft axis from distal to proximal decreases. 
         [0011]    By virtue of the fact that the height of the helix increases from distal to proximal, the trocar sleeve can be inserted particularly gently by means of rotation and simultaneous penetration of the helix into the tissue. As a result of the gradually increasing height of the helix, the tissue in the area of the incision can be gently spread out further in a gradual manner. By virtue of the simultaneous decrease in the pitch of the helix, a quite considerable axial advance can be achieved per revolution at the start of the rotation. Since the height of the helix is still quite low in this area, this can be done in a particularly atraumatic manner. Although the decreasing pitch means that the advance movement per revolution becomes smaller as the insertion proceeds, this permits gentle widening and a gentle rotation of the helix through a tissue, i.e. an abdominal wall. 
         [0012]    When the helix, for example, has been screwed completely through the abdominal wall, the portion of the helix that has the greatest height lies opposite the underside of the abdominal wall. This effectively counteracts a withdrawal of the trocar sleeve by pulling movements of the kind that occur during the manipulation of the trocar housing in a medical procedure. Forces that cause a rotation of the trocar sleeve do not normally occur during such manipulations or medical procedures. 
         [0013]    Thus, the trocar sleeve in the area of the helix can be screwed in without any great danger of harming the patient and, after the helix has been screwed through the abdominal wall, it offers considerable resistance to axially directed withdrawal movements. 
         [0014]    In further embodiments of the invention, seen from distal to proximal, the angle of the proximal flank of the helix with respect to the shaft axis decreases and approaches approximately 90°. 
         [0015]    This measure has the advantage that, after the helix has been screwed through the tissue, a flank lies opposite the underside of the abdominal wall, specifically a flank that extends approximately parallel to the direction of the underside of the abdominal wall, with the result that there is a particularly good blocking action against axial withdrawal in the proximal direction. However, the flank angle in connection with the pitch is still so pronounced that the trocar sleeve can be unscrewed again from the abdominal wall after the medical procedure has been completed. In combination with the maximum height of the helix, a favourably oriented blocking surface is thus available which can come into blocking engagement with the inner face of the tissue of the body cavity. 
         [0016]    In a further embodiment of the invention, the height of the helix increases from zero to a maximum height. 
         [0017]    This measure has the advantage that the trocar sleeve can initially be placed on the corresponding incision and then advanced linearly until the helix begins to rise. From this point, the trocar sleeve in the area of the helix can be screwed easily and relatively atraumtically through the tissue. The increase from the height zero allows the helix to be screwed particularly gently into the opening in the tissue. The maximum height of the helix depends on the size of the trocar sleeve and also on the nature of the intervention, particularly on which attachments and manipulations take place at the proximal end of the trocar and entail the risk of the trocar being withdrawn in the proximal direction. 
         [0018]    In a further embodiment of the invention, the increase in the height of the helix is constant. 
         [0019]    This measure has the advantage that the screwing-in can be carried out particularly smoothly, in particular free of jolts. 
         [0020]    In a further embodiment of the invention, the maximum height of the helix amounts to the extent of the external diameter of the trocar shaft. 
         [0021]    In this height range, the trocar sleeve can be fixed particularly securely against accidental withdrawal. 
         [0022]    In a further embodiment of the invention, the height of the helix, following the maximum height, decreases to zero again within at most a 360° winding. 
         [0023]    This measure has the advantage that, after the area of maximum height has been screwed through, the trocar sleeve can be screwed in slightly further, such that the tissue behind the screwed-in helix can then immediately bear smoothly on the outer face of the shaft. In other words, no step is present at the end of the helix. This measure also makes it easier to unscrew the trocar sleeve after the medical intervention. 
         [0024]    In a further embodiment of the invention, a shaft portion without a thread is present on the distal side of the helix. 
         [0025]    This measure has the advantage that this “smooth” portion without external thread can first of all be applied in a “classical” manner and can be driven axially through the tissue in the distal direction. At this point, a trocar mandrel can also already be withdrawn. When the distal end of the helix has reached the outer face of the tissue, the screwing procedure can begin and the trocar sleeve in the area of the helix can be screwed through the tissue, for example the abdominal wall. It is particularly advantageous here that the helix extends over only a portion of the shaft. 
         [0026]    In a further embodiment of the invention, a retainer, which is movable along the shaft axis and can be placed on an upper face of a tissue through which the trocar sleeve is pushed, can be arranged on the shaft on the proximal side of the helix. 
         [0027]    This measure, which is known per se, can permit improved fixing of the trocar sleeve and, in particular, can additionally prevent the trocar sleeve from accidentally being pushed further in the distal direction. 
         [0028]    This securing could in principle also be achieved by a process in which the helix is not screwed completely through the tissue area, i.e. the abdominal wall, and instead threaded portions of the helix with a relatively large height remain in the area of the opening and bear on the underside and also on the upper face. However, this would place an additional strain on the tissue in the area of the opening through which the trocar sleeve is introduced. 
         [0029]    It is therefore advantageous to screw the entire helix through the abdominal wall, such that only a smooth, thread-free portion of the shaft remains in the area of the tissue opening. A thread-free portion of this kind is therefore provided on the proximal side of the helix. 
         [0030]    In a further embodiment of the invention, the retainer is designed as a disc-like element which is movable along the shaft axis and can be held stationary on the shaft in at least one position. 
         [0031]    This measure has the advantage that the holder can be applied and locked in position particularly easily and especially from the outside, i.e. in a way clearly visible to the person handling the trocar sleeve. 
         [0032]    In a further embodiment of the invention, the retainer has an internal thread which meshes with a corresponding second external thread on the outer face of the shaft, such that the retainer is movable axially to and fro on the proximal side of the helix. 
         [0033]    In a further embodiment of the invention, the retainer is made from a flexible plastic material, and the retainer is movable axially to and fro over a second external thread on the outer face of the shaft. 
         [0034]    This measure has the advantage that, on account of the flexible nature of the material, the retainer can easily be pushed with its opening onto the shaft and can be guided axially in the area of the second external thread. The internal thread in the opening of the retainer can be omitted for manufacturing reasons. A retainer of such configuration can also be pushed onto a shaft without a second external thread and can be moved along same. The opening in the retainer is then of such a dimension that it is slightly widened by the shaft, and the retainer sits on the shaft with a frictional fit and can be moved when the frictional force is overcome. 
         [0035]    The retainer can also be designed as a slit or U-shaped element that can be clipped laterally onto the shaft. 
         [0036]    It is advantageous to provide a thread-free shaft portion in the area between the helix and the second external thread. The tissue can bear gently on this smooth area of the outer face of the shaft. In the slit design of the retainer, the latter can be clipped on laterally in this area. 
         [0037]    It will be appreciated that the aforementioned features and the features still to be explained below can be used not only in the cited combinations but also in other combinations, without departing from the scope of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0038]    The invention is described and explained in more detail below with reference to the attached drawings, in which: 
           [0039]      FIG. 1  shows a perspective view of a trocar sleeve according to the invention without a proximal seal, 
           [0040]      FIG. 2  shows a side view of the trocar sleeve with a proximal seal, 
           [0041]      FIG. 2 a    shows a side view of the trocar sleeve with demonstrating an angle of gradient of the helix, 
           [0042]      FIG. 3  shows a longitudinal section along the line III-III in  FIG. 2  in the area of the helix, 
           [0043]      FIG. 4  shows a cross section along the line IV-IV in  FIG. 2 , 
           [0044]      FIG. 5  shows a cross section along the line V-V in  FIG. 2 , 
           [0045]      FIG. 6  shows a cross section along the line VI-VI in  FIG. 2 , 
           [0046]      FIG. 7  shows a cross section along the line VII-VII in  FIG. 2 , 
           [0047]      FIG. 8  shows a cross section along the line VIII-VIII in  FIG. 2 , 
           [0048]      FIG. 9  shows a partial side view of the trocar sleeve with a trocar mandrel pushed in shortly before placement on an abdominal wall, 
           [0049]      FIG. 10  shows a view corresponding to  FIG. 9 , in a situation in which a distal end portion of the shaft has already been pushed through the abdominal wall and the trocar has been withdrawn, 
           [0050]      FIG. 11  shows a situation comparable to  FIG. 10  as the helix begins to be screwed into the abdominal wall, 
           [0051]      FIG. 12  shows a situation in which the helix has been screwed completely through the abdominal wall, and 
           [0052]      FIG. 13  shows a situation in which a retainer is placed onto the outer face of the abdominal wall. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0053]    A trocar sleeve shown in the figures is designated in its entirety by reference number  10 . 
         [0054]    As can be seen in particular from  FIGS. 1 and 2 , the trocar sleeve  10  has a rectilinearly extending hollow shaft  12 , which has a shaft axis  13 . The shaft  12  is cylindrical and has a cylindrical outer face  22 . 
         [0055]    The shaft  12  has an open distal end  14  and is provided, at its proximal end, with a housing  18  that can be closed in a gas-tight manner by a seal  20  ( FIG. 2 ). As can be seen from  FIGS. 1 and 2 , the outer face  22  is smooth in a distal end portion  24  of the shaft  12 , i.e. has no thread there. 
         [0056]    This distal end portion  24  is adjoined in the proximal direction by a longitudinal portion  25  on which a first external thread  26  is present in the form of a helix  28 , wherein the helix  28  rises from the cylindrical outer face  22  of the shaft  12 . 
         [0057]    The exact design of the helix  28  will first be described and explained in detail in particular in connection with  FIG. 2  and with the sectional views in  FIGS. 3 to 8 . 
         [0058]    In the illustrative embodiment shown, the helix  28  is constructed from a helical winding which has approximately two complete thread turns. 
         [0059]    As can be seen from  FIG. 2 a   , the helix  28  and the respective vertex line of the first outer thread has an angle of gradient with respect to a plane perpendicular to the shaft axis  13 , which changes, seen from distal to proximal, from an acute angle of more than 45 degrees to an angle of less than 20 degrees. The vertex line is the line where all vertices of the helix lie. 
         [0060]    It will be seen from the sectional views in  FIGS. 3 and 4  that, viewed from the distal end  14  in the direction of the proximal end  16 , the helix  28  rises from a height zero through a height H 1  and a height H 2  to a maximum height H 3 . The increase is constant. 
         [0061]    The helix begins at a height zero, then immediately rises to a height of approximately 2.7 mm, has a height of 5 mm in the area of the cross section in  FIG. 5 , and it has a height of 6.5 mm at the level of the cross sections in  FIGS. 6 and 7 . Following the maximum height H 3  of approximately 6.5 mm, the height drops very rapidly again (ca. 90°) to a very low height of approximately 2.7 mm, as is shown in  FIG. 8 . 
         [0062]    The respective heights are indicated in  FIGS. 5 to 8  by the vertices S 5 , S 6 , S 7  and S 8 . 
         [0063]    Turning now to  FIG. 2 , it will be seen that the pitch of the helix decreases continuously from distal to proximal. The pitch is defined by the height difference of two opposite vertices after a 360° rotation. 
         [0064]    The pitch at the start of the helix  28 , i.e. according to the cross section in  FIG. 4 , is 20 mm per revolution, the pitch in the area of the cross section in  FIG. 5  is in the range of 10 mm per revolution, the pitch in the area of the cross section in  FIG. 6  is in the range of 7 mm per revolution, and the pitch in the area of the cross section in  FIG. 7  is only 4 mm per revolution. Following the maximum, the pitch is 8 mm per revolution. 
         [0065]    The term “per revolution” is to be understood as meaning that, if one takes this point and if one were to make a complete revolution, this pitch would result. 
         [0066]    In actual fact, however, the pitch of the helix  28  changes continuously from distal to proximal. 
         [0067]    It will be seen in particular from the sectional view in  FIG. 3  that the angle of the distal flank  48  of the helix  28  remains almost unchanged. 
         [0068]    However, the angle of the flank  50  directed towards the proximal end decreases continuously. The flank angle α of the flank  50  is the angle between the flank  50  and, seen from distal to proximal, the shaft axis  13 . Thus, at the start of the helix, the flank angle α 1  with respect to the shaft axis  13 , seen from distal to proximal, is approximately 140°. This flank angle decreases such that, for example, the flank angle α 2  is approximately 130°. In the area of the last winding, i.e. in the area of the maximum height H 3 , the flank angle α 3  is not quite 100°. 
         [0069]    Overall, the height H of the helix  28  in the shaft portion  25  thus increases from zero to the maximum height H 3  and then drops rapidly. The whole thread turn of the helix  28  includes approximately two complete 360° revolutions. 
         [0070]    At the same time, the pitch decreases, seen from distal to proximal, and the angle of the flank of the helix with respect to the shaft axis  13 , directed towards the proximal end, becomes ever smaller. 
         [0071]    Returning to  FIGS. 1 and 2 , it will first be noted that the shaft portion  25  with the helix  28  is adjoined by a thread-free portion  37 . Following this thread-free portion  37 , a second external thread  30  rises from the outer face  22  of the shaft, but this second external thread is configured as a “regular” external thread with a constant height, constant pitch and constant flank shape. 
         [0072]    A retainer  34  in the form of a triangular disc  36  is received on this second external thread  30 . The retainer  34  is made from a flexible silicone material. The triangular disc  36  can be moved axially in the proximal or distal direction. The triangular shape makes it easier to grip and turn or move the retainer. In the area of its central opening  32 , the flexible silicone material bears, as as result of deformation, on the contour of the second external thread  30 . 
         [0073]    An example of a use of the trocar sleeve  10  according to the invention in laparoscopy will be described with reference to the sequence of  FIGS. 9 to 13 . 
         [0074]    As can be seen from  FIG. 9 , a trocar mandrel  42  is pushed into the inner space of the shaft  12  and its tip  44  extends past the distal end of the trocar sleeve  10 . This tip  44  is placed on an incision  46  on the upper or outer face  41  of an abdominal wall  40 . When this assembly is pushed forward axially, the trocar sleeve  10  is initially pushed via the smooth distal end portion  24  through the abdominal wall  40 , until the helix  28  reaches the upper face  41 , as is shown in  FIG. 10 . The trocar mandrel  42  can now be withdrawn. 
         [0075]    As can be seen from the transition from  FIG. 10  to  FIG. 11 , the helix  28  is now screwed gradually through the abdominal wall  40 . It is therefore the area of the helix  28  provided with the low height but with the high pitch that is first to enter the abdominal wall. The trocar sleeve  10  can thus be screwed in by a certain distance through a 360° revolution, as can be seen from the transition from  FIG. 10  to  FIG. 11 . 
         [0076]    By further rotation of the trocar sleeve  10  about the shaft axis  13 , the helix  28  is screwed in further and all the way through the abdominal wall  40 . This is shown in  FIG. 12 . It is clear that at least one further 360° revolution was necessary for this. The first outer thread  26  has only two complete windings. The overall pitch of the two windings approximately corresponds to the height of the tissue, i.e. the abdominal wall  40  through which the trocar sleeve  10  has to be turned. 
         [0077]    From  FIG. 11  it can be seen that in the direction of the axis relatively large surface areas between the windings  29  and  31  are present, onto which free space, the tissue of the abdominal wall can rest. Less tissue has to be dilated resulting in less stress and turning through of the helix  28  needs less force. Additionally, less torsional stresses act on the shaft during turning. This opens to produce the shaft from a flexible plastic material. This also opens the possibility to form the shaft together with the helix with a blow-mold procedure. 
         [0078]    The proximal flank  50  with the small inclination angle α 3  (see  FIG. 3 ) now lies opposite the underside  43  of the abdominal wall  40 . At the same time, the height H of the helix  28  is at its most pronounced in this area. It is thus clear from  FIG. 12  that the helix  28  offers considerable resistance to an axial movement of the trocar sleeve  10  in the proximal direction. 
         [0079]    This prevents a situation in which, during the usual manipulations, the trocar sleeve  10  is inadvertently withdrawn from the abdominal wall  40 . 
         [0080]    The retainer  34  is provided as an additional safety feature, it being possible for the retainer  34  to be rotated about the second external thread  30  until its underside comes to lie on the upper face  41  of the abdominal wall  40 , as is shown in  FIG. 13 . 
         [0081]    In this position, the trocar sleeve  10  is secured against axial movement both in the proximal direction and also in the distal direction and is also held relatively stable against tilting. It will be seen from  FIG. 13  that the tissue in the area of the opening in the abdominal wall  40  has positioned itself around the thread-free, smooth portion  37  between the end of the helix  28  and the start of the second external thread  30 . That is to say, the tissue is not adversely affected by the two external threads  26  and  30 , not even during protracted interventions. 
         [0082]    After completion of the surgical procedure, the trocar sleeve  10  is unscrewed again from the abdominal wall  40 , this being made easier by the fact that the helix  28  is continued proximally of the maximum elevation to the height zero but with a small pitch.