Abstract:
A medical instrument for cutting tissue has a tubular outer shaft having at least one outer shaft opening provided with at least one outer shaft blade. A tubular inner shaft is rotatable housed in the tubular outer shaft, the tubular inner shaft has at least one inner shaft opening provided with at least one inner shaft blade cooperating in a cutting action with said outer shaft blade. Said at least one inner shaft opening being curved and has a curved longitudinal central axis when viewed on a plane of projection running parallel to said rotation axis.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to a medical instrument for cutting tissue. 
         [0002]    From DE 10 2006 034 756 A1 a medical instrument for cutting tissue is known with a tubular outer shaft which, in the area of its distal end, has at least one outer shaft opening with at least one outer shaft blade, and with a tubular inner shaft which is rotatable about a rotation axis, is received in the outer shaft and, in the area of its distal end, has at least one inner shaft opening with at least one inner shaft blade which, when the inner shaft is moved in rotation, cooperates in a cutting action with the at least one outer shaft blade of the outer shaft. 
         [0003]    Such instruments are used in minimally invasive surgery for detaching tissue in the human or animal body. To do so, the distal end of the shaft is guided to the operating site where the tissue that is to be detached is situated. To detach the tissue, the cutting element is moved in rotation by means of an external or internal drive having a motor. During the rotation, the blade formed on the cutting element cooperates in a cutting action with an edge of the outer shaft opening designed as a blade, by means of the blade of the cutting element passing the blade of the outer shaft opening upon each rotation. To ensure that the tissue to be detached is brought between the interacting blades, the shaft of such instruments is connected to a suction source, the suction effect of which reaches through the shaft as far as the outer shaft opening, in order to suck the tissue to be detached through this opening and into the shaft, such that the blades can detach the tissue. The detached tissue is sucked through the shaft by the partial vacuum. 
         [0004]    The instrument known from DE 10 2006 034 756 A1 mentioned above comprises an outer shaft which, at its distal end, has a triangular or oval-shaped opening provided with a blade. A tubular rotatable inner shaft, at whose distal end a cutting element is formed, is received in the outer shaft. The cutting element has several oval-shaped openings which are likewise provided with a blade and, seen in a circumferential direction, are of different widths. 
         [0005]    The tissue to be detached is sucked into one of the openings of the cutting element rotating in the outer shaft. The tissue is then detached by means of the blade-type edge of the cutting element opening, into which the tissue to be detached is sucked, running past the leading edge of the opening of the outer shaft in the direction of rotation. After the tissue has been detached, it is sucked through the inner shaft to the proximal end of the instrument. 
         [0006]    Since the blade of the cutting element cooperating in a cutting action with the blade of the outer shaft has a convex profile, i.e. an outwardly curved profile, it is found that dense and tough tissue gathers centrally between the two blades and is actually cut off only at the end of a cutting phase, which often results in blockages. The reason for this is that, because of the unfavourable cutting angle that exists from the start of and during most of the cutting phase, this tissue is not in fact detached but instead “pressed” centrally between the two blades, and it is only broken up within a short time at the end of the cutting phase. The high cutting force required during the short cutting time leads to a marked increase in the cutting power that has to be applied at the end of the cutting phase, and this results in uneven loading of the cutting element and therefore adversely affects its smooth running. 
         [0007]    Therefore, the disadvantage of the known instrument is that the tissue to be detached cannot be detached very efficiently, effectively and satisfactorily. 
         [0008]    It is therefore an object of the present invention to develop an instrument of the type mentioned at the outset in such a way that the cutting performance or cutting action is improved. 
       SUMMARY OF THE INVENTION 
       [0009]    According to the invention, this object is achieved by a medical instrument for cutting tissue, comprising a tubular outer shaft having a distal end area, at least one outer shaft opening is provided in said distal end area of said tubular outer shaft, said at least one outer shaft opening having at least one outer shaft blade, a tubular inner shaft having a distal end area and a central longitudinal rotation axis, said tubular inner shaft being received in said tubular outer shaft and being rotatable in said tubular outer shaft about said central longitudinal rotation axis via a drive, at least one inner shaft opening is provided in said distal end area of said tubular inner shaft, said at least one inner shaft opening having at least one inner shaft blade, said at least one inner shaft blade, when said tubular inner shaft is rotated about said rotation axis cooperates in a cutting action with said at least one outer shaft blade, wherein said at least one inner shaft opening being curved and having a curved longitudinal central axis when viewed on a plane of projection running parallel to said rotation axis. 
         [0010]    A considerable advantage of said curved inner shaft opening is that a sabre-like cutting action is afforded by the inner shaft opening having a curved longitudinal axis in a plane of projection running parallel to the rotation axis. 
         [0011]    In other words, that is to say the inner shaft opening has a curved profile when seen in a side view. This profile has the effect that the inner shaft blades are likewise curved and sabre-shaped, as a result of which, in cooperation with the outer shaft blade, the effective cutting phase is prolonged and the cutting action is thus greatly improved. Accordingly, dense and tough fragments of tissue can be detached efficiently and continuously during a cutting procedure. 
         [0012]    In another embodiment of the invention, the longitudinal axis of the at least one inner shaft opening runs along of an arc of a circle. 
         [0013]    This measure has the advantage of resulting in a steady and continuous cutting profile, as a result of which the cutting performance and cutting action are improved and the smooth running of the rotating inner shaft is enhanced. 
         [0014]    In another embodiment of the invention, said distal end area of said tubular inner shaft is being closed by a cap having a distal end point, said at least one inner shaft opening extends into said cap. 
         [0015]    This measure further increases the flexibility to the extent that tissue located in the area of the distal end of the outer shaft, and therefore accessible only with difficulty, can also be sucked in and detached. 
         [0016]    In another embodiment of the invention, the at least one inner shaft opening extends next to said end point. 
         [0017]    If there are several inner shaft openings, this measure has the effect that the inner shaft openings do not intersect one another and also do not run to the same point, and the stability and strength of the inner shaft are thereby increased. 
         [0018]    In another embodiment of the invention, the at least one inner shaft blade of the at least one inner shaft opening has a wedge-shaped cross section with a wedge point that is arranged on an outer face of the inner shaft. 
         [0019]    This measure has the advantage that the cutting characteristics and the cutting action of the instrument according to the invention are further improved by the inner shaft blade tapering to a point. Moreover, depending on the area of use and on the tissue consistency, it is possible to use an instrument with a suitable cutting angle for achieving the maximum cutting efficiency. 
         [0020]    With the wedge points arranged on the outer face of the inner shaft and the inner face of the outer shaft, the sharp wedge edges of both blades can work close together in a cutting action. 
         [0021]    In another embodiment of the invention, the at least one outer shaft blade of the at least one outer shaft opening has a wedge-shaped cross section with a wedge point that is arranged on an inner face of the outer shaft. 
         [0022]    This measure has the advantage that the cutting characteristics and the cutting action of the instrument according to the invention are further improved by the outer shaft blade tapering to a point. Moreover, depending on the area of use and on the tissue consistency, it is possible to use an instrument with a suitable cutting angle for achieving the maximum cutting efficiency. 
         [0023]    In another embodiment of the invention, the inner shaft has three circumferentially offset inner shaft openings. 
         [0024]    This measure has the advantage that several cutting procedures can take place during a complete rotation of the inner shaft. This results in a very high degree of efficiency of the cutting performance and the cutting action. Moreover, depending on the area of use and on the tissue consistency, i.e. depending on the required aggressiveness of the cutting, an instrument with a suitable cutting angle can be used in order to achieve the maximum cutting efficiency. 
         [0025]    In another embodiment of the invention, the width of the inner shaft openings, seen in a circumferential direction, is smaller than the distance between the inner shaft openings. 
         [0026]    This measure contributes further to the stability and strength of the inner shaft at the distal end. 
         [0027]    In another embodiment of the invention, the outer shaft has three circumferentially offset outer shaft openings. 
         [0028]    This measure has the advantage that the cutting performance of the instrument according to the invention can be further improved. An outer shaft with three outer shaft openings can be combined with an inner shaft with three inner shaft openings in order to enhance still further the cutting performance of the instrument according to the invention. This has the effect that many more blades are used and, as a result, more cutting procedures are performed, which also means that more tissue can be detached within a short time. 
         [0029]    In another embodiment of the invention, the inner shaft can be moved in both directions of rotation by means of a motor of the drive. 
         [0030]    Since different pairs of blades cooperate according to the direction of rotation, the cutting profile also changes, as also does the aggressiveness of cutting of the instrument. This measure therefore has the advantage that, depending on the area of use and on the tissue consistency, i.e. depending on the required aggressiveness of the cutting, a suitable direction of rotation can be chosen in order to achieve the maximum cutting efficiency. 
         [0031]    In another embodiment of the invention, the inner shaft can be moved in oscillation over a predefined angle range. 
         [0032]    This measure has the advantage that, on the one hand, two different cutting profiles with different cutting aggressiveness can be carried out in succession, and, on the other hand, the danger of blockage of the inner shaft is further reduced, since the risk of tissue fragments adhering is minimized by the “vibrating” movement. Moreover, in such an embodiment of the instrument according to the invention, the blades work even more efficiently, as a result of which more tissue can be detached more quickly. 
         [0033]    In another embodiment of the invention, a range of said oscillation is defined in that one cutting procedure is carried out upon each excursion of the oscillating inner shaft. 
         [0034]    This measure has the advantage that the excursion is minimized and the number of cutting procedures carried out at a time is maximized. 
         [0035]    It will be appreciated that the aforementioned features and those 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 
         [0036]    The invention is described and explained in more detail below on the basis of a chosen illustrative embodiment and with reference to the drawings, in which: 
           [0037]      FIG. 1  shows a side view, in partial cross section, of a medical instrument for cutting tissue, 
           [0038]      FIG. 2  shows an enlarged view of the distal end portion of the instrument from  FIG. 1 , 
           [0039]      FIG. 3  shows a perspective view of the distal end portion of the inner shaft with three inner shaft openings, 
           [0040]      FIG. 4  shows a cross section along the line A-A in  FIG. 2 , 
           [0041]      FIGS. 5A-5C  show a cutting procedure with three different positions of the inner shaft opening according to the illustrative embodiment from  FIG. 1  and  FIG. 2 , and 
           [0042]      FIGS. 6A-6C  show a cutting procedure with three different positions of the inner shaft opening according to a further illustrative embodiment. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0043]    A medical instrument shown in the figures, and used for cutting tissue, is designated in its entirety by reference number  10 . 
         [0044]    The medical instrument  10  comprises a tubular outer shaft  12  which, at its proximal end, is connected to a housing  16 . 
         [0045]    In its rounded and closed distal end  18 , the outer shaft  12  comprises one outer shaft opening  20 . The outer shaft opening  20  is formed by a circumferentially and axially limited opening of approximately oval shape being made in a wall  22  of the outer shaft  12 , as can be seen from  FIG. 1  in conjunction with  FIG. 5 . 
         [0046]    A tubular inner shaft  24  is received in the outer shaft  12 , in such a way as to be able to rotate therein about a central longitudinal rotation axis  26 , and is connected at the proximal end to a motor  30  of a drive via a drive shaft  28 . The drive shaft  28  is moved in rotation by the motor  30  according to the rotation arrow  32 , and the rotary movement of the drive shaft  28  is transmitted to the inner shaft  24 , which is moved in rotation relative to the stationary outer shaft  12 . 
         [0047]    An outer diameter of the tubular inner shaft  24  corresponds approximately to an inner diameter of the tubular outer shaft  12 . 
         [0048]    It will further be noted that the motor  30  can also be configured such that the inner shaft  24  can additionally be moved in the direction counter to the rotation arrow  32  or in oscillation in both directions. 
         [0049]    At the distal end  18 , in the area of the outer shaft opening  20  of the outer shaft  12 , the inner shaft  24  has an inner shaft opening  34 . The inner shaft opening  34  extends along a curved longitudinal axis  36  and has an elongate sabre shape, as can be seen in detail from  FIG. 2 . The curved course of the longitudinal axis  36  results from projecting the longitudinal axis  36  onto a plane of projection  37  running parallel to the rotation axis  26 . 
         [0050]    Moreover, the instrument  10  is connected to a suction source  40  via a suction nozzle  38  of the housing  16 . With the suction source  40  switched on, a suction stream forms through the inner shaft  24  to as far as the inner shaft opening  34 , which stream is directed from the inner shaft opening  34  to the suction nozzle  38 . 
         [0051]    As can be seen from the enlarged view in  FIG. 2 , the inner shaft  24  has a first inner shaft blade  42 , which leads in the direction of rotation, and a second inner shaft blade  44 , which trails in the direction of rotation. In the illustrative embodiment shown, the second inner shaft edge  44  cooperates in a cutting action with the outer shaft  12 , as will be described in detail below in the description of  FIGS. 5 and 6 . 
         [0052]      FIG. 3  is a perspective view of the distal end  18  of the inner shaft  24  from  FIG. 1  and  FIG. 2 . 
         [0053]    The inner shaft  24  has three circumferentially offset inner shaft openings  34 . 1 ,  34 . 2 ,  34 . 3 . The inner shaft openings  34 . 1 ,  34 . 2 ,  34 . 3  extend as far as a distal end face  46  shaped as a cap, specifically next to a distal end point  48  of the cap. The end point  48  forms the apex of the distal end  18 , such that they neither intersect each other nor run to the distal end point  48 . As has already been described above, this design leads to increased stability and increased strength of the inner shaft  24  at the distal end  18 . 
         [0054]    It will also he noted that the outer shaft  12 , which cooperates with an inner shaft  24  of this kind, can also have three circumferentially offset outer shaft openings  12 . 1 ,  12 . 2 ,  12 . 3 , in order to further increase the cutting performance. 
         [0055]    In the sectional view shown in  FIG. 4 , along section line A-A from  FIG. 2 , the first and second inner shaft blades  42 ,  44  of the inner shaft opening  34  each have a wedge-shaped cross section with a wedge point arranged close to an outer face  49  of the inner shaft  24 , in order to increase the aggressiveness of the cutting. Moreover, the outer shaft opening  20  has a first outer shaft blade  50  and a second outer shaft blade  52 , which are likewise wedge-shaped and each have a wedge point arranged at the level of the inner face  53  of the outer shaft  12 . The aggressiveness of the cutting can be increased still further by this means. 
         [0056]    A rotation arrow  32 ′ indicates the possibility that the inner shaft  24  can move in both directions of rotation, such that a cutting procedure for cutting a tissue  54  can be performed on both outer shaft blades  50 ,  52 . In the illustrative embodiment shown, the inner shaft  24  rotates in the clockwise direction, such that the second inner shaft blade  44  cooperates in a cutting action with the first outer shaft blade  50  and the tissue  54  can be efficiently detached. 
         [0057]    Upon rotation in the opposite direction, e.g. during an oscillating movement, the first inner shaft blade  42  and the second outer shaft blade  52  cooperate analogously in a cutting action and generate the corresponding cutting procedure. 
         [0058]    The use of the medical instrument  10  from  FIG. 1  will be explained in brief on the basis of the sequence of  FIGS. 5A-C  and  6 A-C. 
         [0059]      FIG. 5  and  FIG. 6  illustrate the advantageous cutting profile and the improved cutting action of the instrument according to the invention on the basis of the curved, sabre-shaped inner shaft blade  44 . Three positions A, B, C of the inner shaft  24  during the passage of the inner shaft opening  34  through the outer shaft opening  20  are shown in each case. The outer shaft opening  20  is oval-shaped ( FIG. 5 ) or elongate ( FIG. 6 ). As soon as the inner shaft opening  34  has passed the outer shaft opening  20 , a suction area  56  forms, which is indicated as a cross-hatched area, and the tissue  54  is sucked into this area by the suction current generated by the suction source  40 . By means of the suction effect present in the suction area  56 , the tissue  54  to be detached is sucked in through the outer shaft opening  20  and the inner shaft opening  34 . As the second inner shaft blade  44  of the inner shaft  24  runs past the first outer shaft blade  50  of the outer shaft  12 , as can be seen from  FIGS. 5 and 6 , the tissue  54  that is to be detached, and that has been sucked in, is cut off. The detached tissue  54  is sucked through the inner shaft  24  to the proximal end of the instrument  10 . 
         [0060]    The cutting angle  58  arising during a cutting procedure between the rear, and therefore cutting, second inner shaft blade  44  and the first outer shaft blade  50  cooperating therewith varies throughout the movement of the inner shaft opening  34  past the outer shaft opening  12 . 
         [0061]      FIG. 5A  and  FIG. 6A  show the “suction phase” during which tissue  54  is only sucked in, since there is virtually no cutting action because of the obtuse cutting angle  58 . As is evident from  FIG. 5B  and  FIG. 6B , the “cutting phase” of the instrument according to the invention, compared to the prior art described at the outset, begins at a very early stage and with an advantageously acute cutting angle  58 . The curved second inner shaft blade  44  thus cooperates very effectively with the first outer shaft blade  50  and in so doing cuts through the tissue  54  like a sabre. Finally,  FIG. 5C  and  FIG. 6C  show the “end phase” in which it is clear that the acute cutting angle slowly and continuously shrinks during the passage, thus imitating the cutting profile of slowly closing shears, for example anvil shears, and providing a more efficient cutting action during a longer cutting phase in relation to the tissue  54  that is to be removed.