Abstract:
The invention relates to a medical instrument comprising an elongated element, which is preferably configured for transoral placement in a stomach, and an end effector ( 100 ) arranged at one end of the elongated element, wherein the end effector ( 100 ) can be operated by means of a hydraulic operating mechanism ( 1 ), wherein the hydraulic operating mechanism ( 1 ) comprises a cylinder ( 20 ) having at least one, preferably two, three, four, or five, overflow channels ( 21   a,    21   b,    21   c,    21   d ) for a hydraulic fluid, which are connected to the cylinder interior by means of at least one bore ( 22, 22   b,    22   b′,    22   c,    22   c′,    22   d,    22   d ′), a piston ( 30 ) arranged in the cylinder ( 20 ) and movable along the longitudinal axis of the cylinder ( 20 ) is provided, wherein the piston ( 30 ) divides the interior ( 23 ) of the cylinder ( 20 ) into a first cylinder chamber ( 23   a ) and a second cylinder chamber ( 23   b ) and is connected to the end effector ( 100 ) by means of a piston rod ( 31 ), and at least one connection ( 41 ) for introducing hydraulic fluid into the first cylinder chamber ( 23   a ) and at least one further connection ( 41   a,    41   b,    41   c,    41   d ), which is connected to at least one overflow channel ( 21   a,    21   b,    21   c,    21   d ) of the cylinder ( 20 ), are provided.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a medical instrument which includes an elongated element preferably configured for transoral placement in a patient&#39;s stomach, and an end effector which can be positioned at one end of the elongated element and can be operated by means of a hydraulic actuating mechanism. The invention also relates to a method of operating the end effector which is attached in particular at one end of an endoscopic system. 
     2. The Prior Art 
     DE 44 35 644 B1 describes a hydraulic bending mechanism for a bending section of an endoscopic system. A similar device can also be found in EP 0 401 129 A1. 
     In U.S. Pat. No. 4,485,817 A there is disclosed a hydraulic bending mechanism for an end effector, where one piston is moved against a second piston to build up the pressure necessary in the hydraulic fluid for operating the end effector. Disadvantages of this hydraulic actuating mechanism are its complicated construction and the fact that this actuating mechanism can control only two defined operational states of the end effector. Stomach plication however will often require more than two operational states of the end effector, which makes the actuating mechanism unsuitable for such end effectors. A similar device is described in U.S. Pat. No. 5,361,583 A. 
     It is therefore the object of the present invention to provide a medical instrument with a hydraulic actuating mechanism which is simple in design and safe in operation and avoids the disadvantages of the state of the art. 
     SUMMARY OF THE INVENTION 
     The invention achieves this object by providing a medical instrument of the above-mentioned kind wherein the hydraulic actuating mechanism comprises a cylinder with at least one, preferably two, three, four or five, overflow passages for a hydraulic fluid which are connected to the interior of the cylinder by at least one bore, and where a piston movable along the longitudinal axis of the cylinder is provided in the cylinder, the piston partitioning the cylinder interior into a first cylinder space and a second cylinder space and connecting via a piston rod to the end effector, and where at least one fitting is provided for feeding hydraulic fluid into the first cylinder space and at least one further fitting is provided which is connected to at least one overflow passage of the cylinder. 
     In a first variant of the invention the overflow passages are configured as grooves on the outer wall of the cylinder and connect to the interior space of the cylinder by means of bores which are positioned at different distances from one end of the cylinder. Preferably, the cylinder is inserted into a sleeve, such that the overflow passages between the inner wall of the sleeve and the outer wall of the cylinder are formed by the grooves on the outer cylinder wall. 
     The fittings for the hydraulic fluid which connect to the interior space of the cylinder are preferably placed in a sealing element which is located at the end of the sleeve facing away from the piston rod, resulting in a compact and reliable hydraulic actuating mechanism. 
     In an alternative variant of the invention at least one overflow passage is located within the cylinder wall and connects to the cylinder space via at least one bore. While this variant will be more expensive to manufacture than the one above, it will not require a separate sealing element since the fittings for the hydraulic fluid are placed directly in the cylinder bottom. This will result in a smaller size of the instrument, which is important especially for endoscopic applications. 
     If hydraulic fluid is fed via the fitting connected to the adjacent first cylinder space, the piston moves forward away from the cylinder bottom and hydraulic fluid flows out of the second cylinder space via the second fitting, which is connected to the second cylinder space through an overflow passage. The volume of the first cylinder space increases while the volume of the second cylinder space decreases, and the piston rod of the piston is pressed out of the cylinder. When the at least one bore of the overflow passage is closed by the piston skirt of the piston in the cylinder, the piston can no longer move due to the counter-pressure in the second cylinder space and a defined position of the piston has been reached. This position of the piston corresponds to a defined operational state of the end effector connected to the piston rod. In accordance with the number and position of the overflow passages, respectively bores of the overflow passages, different operational states of the end effector connected to the medical instrument of the invention can be defined. 
     For controlling an end effector with two gripping elements as used in stomach plication, three operational states are required: a first closed state for positioning the end effector in the stomach of the patient, for instance; an opened state in which tissue is positioned between the gripping elements by moving these gripping elements against each other and finally a second closed state in which a staple device stitches together the tissue held between the gripping elements of the end effector. A suitable end effector may for instance be found in EP 2 187 559 A1 or in US 2004/59349 A1. 
     A preferred variant of the invention, which is particularly suitable for end effectors used in stomach plication, thus is provided with four overflow passages, three of which control the above-mentioned three operational states of the end effector, while the fourth overflow passage effects complete pressure relief in the second cylinder space. 
     Other end effectors may of course also be connected to the medical instrument of the invention; for such purposes a standardized adaptor element is preferably provided on the medical instrument. The end effectors connected to the hydraulic system of the invention may be diverse gripping elements, but also probes and other endoscopic and/or endosurgical elements. 
     To operate the hydraulic actuating mechanism of the invention a hydraulic aggregate is provided, which cooperates with the hydraulic actuating mechanism and comprises at least one pump and at least one hydraulic line leading to each fitting of the sealing element, each hydraulic line containing preferably at least one switching element. 
     Furthermore the object of the invention is achieved by an endosurgical instrument, especially an endoscope, comprising an elongated element which is preferably configured for transoral placement in the stomach, and an end effector placed at one end of the elongated element, which end effector is hydraulically actuated by means of the device according to the invention. 
     The end effector preferably has two claw-shaped gripping elements which can be moved from an open position to at least one, and preferably two or more, dosed position(s). 
     In a method according to the invention for actuating an end effector, in particular an end effector located at the tip of an endosurgical instrument, the position of a piston with a piston rod within a cylinder is changed with the use of a device according to the invention by the inflow of hydraulic fluid into a first cylinder space and/or the outflow of hydraulic fluid out of a second cylinder space, the piston position determining the operational state of the end effector which is connected to the piston rod. 
     Due to its space-saving design, the medical instrument of the invention can also be used with known endoscopic systems. The diameter of the medical instrument according to the invention can be kept small enough to place it in the channel of a state-of-the-art endoscope, for instance. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described in more detail below with reference to the enclosed drawings of variants, which are not to be interpreted as restrictive. There is shown in 
         FIG. 1  an exploded view of the hydraulic actuating mechanism according to the invention; 
         FIG. 2   a  a first sectional view of the actuating mechanism of  FIG. 1  in the assembled state; 
         FIG. 2   b  a second sectional view of the actuating mechanism rotated by 90° relative to the view of  FIG. 2   a;    
         FIG. 2   c  a view of the actuating mechanism as seen from the side of the sealing element; 
         FIG. 2   d  a view of the actuating mechanism as seen from the side of the piston rod; 
         FIG. 3   a  a sectional view of the actuating mechanism with end effector; 
         FIG. 3   b  a side view of the actuating mechanism with end effector of  FIG. 3   a;    
         FIG. 3   c  an axonometric view of the actuating mechanism with end effector of  FIG. 3   a;    
         FIG. 4   a  a schematic hydraulic circuit for the opened end effector according to  FIGS. 3   a  to  3   c;    
         FIG. 4   b  the opened end effector of  FIG. 3   a  with cover in an axonometric view; 
         FIG. 5   a  a schematic hydraulic circuit for the end effector in a first closed state; 
         FIG. 5   b  an axonometric view of the end effector in a first closed state; 
         FIG. 5   c  a view from above of the end effector of  FIG. 5   b;    
         FIG. 6   a  a schematic hydraulic circuit for the end effector in a second closed state; 
         FIG. 6   b  an axonometric view of the end effector in a second closed state; 
         FIG. 6   c  a view from above of the end effector of  FIG. 6   b;    
         FIG. 6   d  a schematic hydraulic circuit for opening of the end effector from the second closed state; 
         FIG. 7   a  a partial sectional view of another end effector; 
         FIG. 7   b  an axonometric view of the end effector of  FIG. 7   a;    
         FIG. 7   c  a schematic hydraulic circuit for the end effector of  FIG. 7   a ; and 
         FIGS. 8   a ,  8   b  two partially cut views of a restoring device. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  shows in an exploded view the hydraulic actuating mechanism  1  of the invention, in particular for an endosurgical and/or endoscopic instrument. It has a sleeve  10  into which a cylinder  20  may be inserted. In the variant shown the cylinder  20  is provided with four overflow passages  21   a ,  21   b ,  21   c ,  21   d , which are configured as grooves in the outer wall of the cylinder  20  in parallel with the longitudinal axis A of the cylinder and are connected to the interior  23  ( FIGS. 2   a ,  2   b ) of the cylinder  20  via bores  22   a ,  22   b ,  22   b ′, 22   c ,  22   c ′,  22   d ,  22   d ′. Furthermore, the hydraulic actuating mechanism  1  comprises a piston  30  with a piston rod  31  and a sealing piston skirt  32 , which can move in the cylinder  20  along its longitudinal axis A. Finally, there is provided a sealing element  40 , which has five fittings  41 ,  41   a ,  41   b ,  41   c ,  41   d , configured as bores for supplying hydraulic fluid through the sealing element  40 . 
     In  FIGS. 2   a  and  2   b  the hydraulic actuating mechanism  1  is shown in its assembled state. The cylinder  20  sits in the sleeve  10  and is held in position by the sealing element  40 . Sleeve  10 , cylinder  20  and sealing element  40  are arranged relative to each other in such a way that the hydraulic fittings  41   a ,  41   b ,  41   c ,  41   d , of the sealing element  40  are aligned to connect to the overflow passages  21   a ,  21   b ,  21   c ,  21   d , said passages  21   a ,  21   b ,  21   c ,  21   d , being connected via the bores  22   a ,  22   b ,  22   b ′,  22   c ,  22   c ′,  22   d ,  22   d ′ to the interior of the cylinder  20 . 
     The piston  30  is placed in the interior of the cylinder  20 , its piston rod  31  being guided through a central opening  11  of the sleeve  10 . On its piston skirt  32  within the cylinder  20  the piston  30  is provided with sealing means  33 , which surround the piston skirt  32  in the form of rings and, when the piston  30  is in an appropriate position within the interior  23  of the cylinder  20 , close at least one of the overflow passages  21   a ,  21   b ,  21   c ,  21   d  ( FIG. 2   a ). Another sealing means  13  is provided in the concentric opening  11  of the sleeve  10  to prevent leaking of the hydraulic fluid from the cylinder  20 . 
       FIG. 2   c  is a view from above of the hydraulic actuating mechanism  1 , where essentially the sealing element  40  is visible. One can see that, surrounding the central hydraulic fitting  41 , four other fittings  41   a ,  41   b ,  41   c ,  41   d  are provided on the essentially square sealing element  40 . In the corners of the sealing element  40  there are provided further openings  42 , which receive fastening means (not shown) for attaching the sealing element  40  to the sleeve  10 .  FIG. 2   d  finally shows the hydraulic actuating mechanism  1  of the invention as seen when looking in the direction of the piston rod  31 . 
       FIGS. 3   a  to  3   c  show the actuating mechanism  1  with an attached end effector  100 , as used especially for endosurgery.  FIG. 3   a  shows that the end effector  100  is positioned on the piston rod  31  of the piston  30 , with the end effector  100  being in an “open” state as shown in  FIG. 3   b . The end effector  100  has two claw-like gripping elements  110   a ,  110   b , the gripping element  110   a  carrying a first part  120   a  of a staple element, which comprises two pins  121  on a plate element  122   a . A staple device of this kind is for instance disclosed in Austrian patent A 239/2009 of the applicant. 
     When the two gripping elements  110   a ;  110   b  of the end effector  100  are closed with the help of the hydraulic actuating mechanism  1  according to the invention, the first part  120   a  of the staple device meshes with the second part  122   b  of the staple device carried in the second gripping element  110   b , for instance to fixate tissue in stomach plication. In order to be able to move the two gripping elements  110   a ,  110   b  towards each other or away from each other, guiding elements  111   a ,  111   b  are provided, which move along guiding grooves  112   a ,  112   b  when the piston  30  of the hydraulic actuating mechanism  1  is moved. In  FIG. 3   a  the piston  30  is shown in its bottom position, where it essentially rests against the sealing plate  40 . When the piston  30  is moved upwards by the hydraulic fluid entering through the central bore  41  of the sealing element  40 , the guiding elements  111   a ,  111   b  are moved along the guiding grooves  112   a  in the direction towards the gripping elements  110   a ,  110   b , thereby causing them to approach each other as required by the shape of the guiding grooves  112   a ,  112   b . A curved shape of the guiding grooves  112   a ,  112   b  has the advantage that little force is necessary to reach a first closing position of the end effector  100 , while in the second closing position the larger force required for breaking the pins  121  is provided due to the special shape of the guiding grooves  112   a ,  112   b . Depending on the respective application the shape of the guiding grooves  112   a ,  112   b  may be chosen straight or curved. 
     The functioning of the hydraulic actuating mechanism  1  according to the invention will now explained in more detail.  FIGS. 4   a  to  6   d  schematically present a hydraulic system  200  suitable for operating the hydraulic actuating mechanism  1 . The hydraulic system  200  comprises a pump  201 , which feeds hydraulic fluid to the hydraulic actuating mechanism  1 , via a first hydraulic line  202  connected to a first cylinder space  23   a . Furthermore, the overflow passages  21   a ,  21   b ,  21   c ,  21   d  are connected to other hydraulic lines  202   a ,  202   b ,  202   c ,  202   d  and are thus connected to a container  203  for hydraulic fluid. Each hydraulic line  202 ,  202   a ,  202   b ,  202   c ,  202   d  is provided with at least one switching element  204 , for instance a hydraulic valve, permitting or inhibiting the flow of hydraulic fluid in the respective hydraulic line  202 ,  202   a ,  202   b ,  202   c ,  202   d . In certain cases it is of advantage for the correct actuation of the end effector  100  to provide an additional restoring element  210 , which is described in detail in  FIGS. 8   a  and  8   b.    
       FIG. 4   a  presents the switching state in which the piston  30  of the hydraulic actuating mechanism  1  is shown in its bottom position immediately adjacent to the sealing plate  40 . Detailed presentation of the sealing plate  40  and the connected hydraulic lines is suppressed here to keep the drawing clear and uncluttered. The hydraulic lines  202 ,  202   a ,  202   b ,  202   c ,  202   d  are shown directly connected to points on the overflow passages  21 ,  21   a ,  21   b , whereas they are actually connected to the fittings on the sealing plate  40 , as shown in the variant of the invention of  FIGS. 1 to 2   d . The hydraulic scheme of  FIG. 4   a  shows the state of the hydraulic system  200  in which the end effector is opened, as depicted in  FIGS. 3   a  to  3   c , respectively  FIG. 4   b . In  FIG. 4   b  the end effector  100  of  FIG. 3   a  is shown with its cover  101 , for instance made of silicone. 
     The hydraulic actuating mechanism  1  is especially suitable for the operation of end effectors which are used in endoscopic stomach plication. In endoscopic stomach plication an end effector  100  is introduced into the stomach by means of an endoscope and subsequently actuated in such a way that a staple device contained in the end effector  100  (as for instance shown in  FIGS. 3   a  to  3   c ) is placed in the (stomach) tissue. During the insertion of the endoscope into the stomach the end effector must be closed to avoid injury of the oesophagus or the stomach. On the other hand the end effector  100  must not be closed to such an extent that the pins  121  of the staple device lock with the second plate-shaped part  112   b.    
     In  FIGS. 5   a  to  5   c  the first closed state of the end effector  100 , in which the preferably transoral placement of the end effector at the chosen site is carried out, is shown together with the corresponding hydraulic scheme. In this case the piston  30  is in an intermediate position within the cylinder  20  and partitions the cylinder interior into two cylinder spaces  23   a  and  23   b . When the end effector  100  has been placed at the chosen site, for instance in the stomach, the two gripping elements  110   a ,  110   b  are moved to the opened position as in  FIG. 4   b.    
     By the subsequent closing of the gripping elements  110   a ,  110   b  the stomach tissue is gripped by the gripping elements  110   a ,  110   b  and penetrated by the pins  121 . Finally, the piston  30  is moved to its uppermost position, as shown in  FIGS. 6   a  to  6   c , and the pins  121  of the staple device break at the predetermined breaking points (not shown). 
     After the end effector  100  has been opened by moving the piston  30  to its bottom position immediately adjacent to the sealing element  40  ( FIG. 6   d )—the hydraulic fluid flowing via the overflow passage  202   d  into the second cylinder space  23   b ,—the staple device remains in the tissue, and the end effector  100 , again in the first closed position as in  FIGS. 5   b  and  5   c , may be retracted from the stomach through the oesophagus and the oral cavity. 
     It is obvious that use of the hydraulic actuating mechanism  1  of the invention is not limited to the depicted end effector  100 , but that the hydraulic mechanism  1  may also be used with other end effectors, in particular for medical purposes, which conventionally are actuated by means of Bowden cables or other pulling or pushing elements. 
     Pincer-like end effectors  100  for instance, as shown in  FIGS. 7   a  and  7   b , may also be operated with the actuating mechanism  1  of the invention. The hydraulic system  200  shown in  FIG. 7   c  is somewhat simpler, since only two positions of the end effector, i.e., an open and a closed position, need to be controlled. For this reason the hydraulic actuating mechanism  1  is provided with only one overflow passage  21  in this variant, while the sealing element  40  has one hydraulic fitting  41  for pressure generation in the interior  23  of the cylinder  20  and one hydraulic fitting  41   a  which connects to the overflow passage  21 . Of course, the hydraulic actuating mechanism as described above with more than one overflow passage could also be used. 
     In the dosed position of the pincer-like end effector  100  of  FIGS. 7   a  and  7   b  the piston  30  is in the upper position. In order to open the pincer  100  the piston  30  is moved to its lower position by opening the overflow passage  21 , such that the piston skirt  32  is immediately adjacent to the sealing element  40 . Since this kind of end effector  100  is used especially during surgery to hold and/or fixate tissues over a prolonged period of time, the holding force of the end effector will deteriorate with the passing of time, especially so in mechanisms with Bowden cables, and in the worst case its grip on the tissues may be lost. Therefore an additional restoring element  210  is preferably provided, which by spring-action upholds the hydraulic pressure necessary for the correct functioning of the end effector  100 . 
       FIGS. 8   a  and  8   b  show a preferred variant of an additional restoring element  210 . The restoring element  210  comprises a spring element  211 , here a helical spring, and a turning knob  212 , for adjusting the spring force to the desired level. Via a sealing plate  240  with a hydraulic fitting  241  the restoring element  210  is connected to the hydraulic system and may be activated by means of the switching element  214  ( FIG. 7   c ), if required. It should be evident that this restoring element could also be used with diverse other kinds of end effector. 
     Additionally or as an alternative solution a signalling device may be provided, which signals a pressure drop within the hydraulic system  200 , whereupon the restoring element  210  may be activated by the user. 
     Clearly, the invention is not restricted by the embodiments described here. In particular, the number and position of overflow passages can be adapted as required, more than five overflow passages being possible.