Abstract:
A surgical stapler comprises an elongate housing  10  and a surgical staple  14  slidable longitudinally within the housing towards the free forward end thereof. The back  18  of the staple has a rearward extension  22.  An actuator  16  is slidable forwardly within the housing for driving the staple towards the free end of the housing. An upstanding flange  30  on the extension  22  engages a stop  32  within the housing to restrain the back of the staple against forward movement of the actuator bends the staple to bring the free ends of the legs towards one another to close the staple. Further movement of the actuator then ruptures the join between the extension and the back of the staple to release the closed staple.

Description:
FIELD OF THE INVENTION 
     This invention relates to a surgical stapling device. 
     BACKGROUND 
     Surgical stapling devices have been in existence for many years. They are routinely used in surgical procedures mainly for the purposes of effecting a wound closure. Some of the most popular applications include closing a skin incision end-to-end or end-to-side anastomosis of internal (generally tubular) vessels such as the large bowel, etc. Current staplers are designed to deliver one or more staples in a serial fashion or a number of staples in one shot. Skin staplers, for example, deliver 30 or more staplers in a serial fashion. The staples are stacked within the device and during the firing operation one staple is advanced from the stack and delivered through the head of the device. During the following cycle another staple is advanced from the top of the stack and again delivered through the head of the device and so on. In one shot devices such as a bowel anastomosis stapler the staples are prearranged in a linear or circular fashion and upon activation of the device all the staples are delivered through the head. Examples of existing prior art as described above include U.S. Pat. Nos. 4,592,498, 5,289,963, 5,433,721 and 5,470,010. 
     The mechanism involved in forming a staple and releasing it from its forming mechanism is common to the majority of surgical stapler devices. Generally the components include an anvil, a staple closing actuator, and a staple release mechanism. The anvil is normally positioned in front of the staple and the actuator directly behind the staple. As the actuator advances the staple against the anvil the back section of the staple deforms around both ends of the anvil thereby transforming the staple from a generally U-shape to a generally rectangular shape. At this point the actuator generally retracts and the staple is released from the anvil either as a result of the anvil moving out of position and allowing the staple to move forward, or alternatively ejecting the staple over the anvil thereby releasing it from the device. 
     There are a number of problems associated with the mechanism as described above. Firstly, as the anvil is normally positioned in front of the staple it naturally becomes trapped between the back of the staple and the tissue into which it is being delivered causing the staple back to be spaced away from the tissue as opposed to lying tightly on its surface. This is a particular problem in the field of vascular puncture closure when it is desirable to keep the legs of the staple as short as possible so as to avoid having the legs of the staple within the vessel lumen. 
     Secondly, the method of releasing the staple from the anvil can be both complicated and unreliable. Metal springs are normally used which eject the staple over the anvil thereby affecting its release. However, should the spring fail to operate or is prohibited from operating properly by virtue of some tissue blockage etc, the device will become trapped in-situ. 
     Alternative release mechanisms include mechanical means of moving the anvil so that it is no longer in the path of the staple as it releases from the device. Again this generally involves very small metal components with relatively small movements which can fail to operate thereby leaving the staple trapped within the device and attached to the tissue into which it has been delivered. 
     Therefore there is a need for an improved surgical stapling device which will facilitate closer approximation of the staple back onto the surface of the vessel into which the staple is being delivered and a method of deforming the staple which does not include the use of an anvil component and therefore will not require the use of other components or mechanisms to facilitate the release of the staple from the anvil. 
     SUMMARY OF THE INVENTION 
     According to the present invention there is provided a surgical stapling device comprising an elongate housing, a surgical staple slidable longitudinally within the housing towards a free forward end thereof, the staple having a back and two forwardly pointing legs, an actuator slidable forwardly within the housing for driving the staple towards the free end of the housing, means for restraining the back of the staple against forward movement beyond a predetermined point such that further forward movement of the actuator bends the staple to bring the free ends of the legs towards one another to close the staple, and means for releasing the closed staple, wherein the back of the staple has a rearward extension and the restraining means comprises means for restraining the extension. 
     In a preferred embodiment the rearward extension is rupturably joined to the back of the staple, the staple being released by forward movement of the actuator beyond the point at which the staple is closed while the extension is restrained, thereby to rupture the join. 
     In another preferred embodiment a rearward extension is created which is integral to the staple back. This rearward extension creates a slot into which one end of an extension component is connected. Once the former has formed the staple around the anvil the extension is released from the staple during rearward movement of the former. 
     The benefits of the invention over conventional stapling devices is that, firstly, as no anvil is required the staple can be advanced forward to a position where the staple back is in direct contact with the tissue being stapled. This is of particular advantage when the staple legs must remain short but the level of penetration into the tissue must be assured. Secondly, because there is no anvil component involved in the delivery mechanism, there is no requirement to add additional components so as to facilitate ejection of the staple over or around the anvil component or alternatively to move the anvil component to a position which allows the staple to advance forward and free up the device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a staple with a restraining plate for use in an embodiment of the invention; 
         FIGS. 2(   a ) to  2 ( d ) are plan views (left hand column) and equivalent sectional views (right hand column) of a stapling device according to the embodiment in successive stages of operation; 
         FIG. 3  is a perspective view of the staple and actuator assembly of  FIG. 2 ; 
         FIG. 4  is a perspective view of the forward tip of the actuator of  FIG. 2 ; and 
         FIGS. 5 to 12  are perspective view of further embodiments of staple for use with a device according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the drawings the same reference numerals have been used for the same or equivalent parts. 
     Referring to  FIGS. 1 to 4 , a surgical stapling device comprises an elongated housing or shaft  10  having upper and lower halves  10   a  and  10   b  defining between them a longitudinal channel  12  for slidably accommodating a staple  14  and a staple closing actuator  16  (in the plan views in the left hand column of  FIG. 2  only the lower housing half  10   b  is shown). Only the free forward end of the housing  10  is shown in the drawings, since that is where the invention lies in the present embodiment. The rear end of the housing  10  is preferably formed with a pistol grip and the movement of the various components to be described may be effected by a trigger acting through a cam system. Such an arrangement is described in Irish Patent Application S2000/0722 which may be readily adapted to operate the device of the present embodiment. 
     The staple  14  is generally U-shaped, having a back  18  and two forwardly pointing legs  20 . The free ends of the staple legs  20  are sharpened for ease of tissue penetration. Integral with the staple back  18  there is a rearwardly extending plate  22  which is attached to the upper edge of the centre section  18   a  of the staple back by a pair of narrow, relatively weak tabs  24 . The tabs are effectively thin metal bridges which connect the staple back to the plate  22 . At the rear end of the plate  22  there is an upstanding flange  30  perpendicular to the plane of the plate  22 . In this embodiment the staple  14  including the plate  22  and flange  30  is made as an integral structure from stamped and bent sheet metal stock, for example, a malleable metal or metal alloy such as stainless steel or titanium. 
     Adjacent to the tabs  24 , at the junctions  26  between the centre section  18   a  and the outer sections  18   b  of the staple back on either side, and where in use the staple back is designed to bend through an angle of 90° as will be described, local deformation of the material of the staple is provided so as to ensure that bending takes place preferentially at those points. 
     The actuator  16  is an elongated rod having a forward end which is forked to provide two arms  28  separated by a recess  34 . The lateral separation of the arms  28  is slightly greater than the distance between the junctions  26  on the back  18  of the staple. 
     The device is assembled ( FIG. 2 ) with the actuator  16  extending longitudinally in the channel  12  with its forked end facing towards the free forward end of the housing  10 . The staple  14  is positioned freely in front of the actuator  16  with its back  18  transverse to the axis of the housing  10  with the plate  22  extending rearwardly across the top surface of the actuator. The flange  30  extends up into a recess  32  in the top housing half  10   a.  The actuator arms  28  are behind and in alignment with the outer sections  18   b  of the staple back. 
     In use, both the staple  14  and the actuator  16  are initially retracted,  FIG. 2(   a ), so that the flange  30  is adjacent the rear end of the recess  32  and the entire staple  14  is contained wholly within the housing  10 . Upon operation of the trigger previously mentioned, or other operating mechanism, the actuator  16  is driven forwardly towards the free forward end of the housing  10 . This drives the staple  14  before it by engagement of the actuator arms  28  with the outer sections  18   b  of the staple back. 
     At a predetermined point,  FIG. 2(   b ), where the back of the staple is substantially level with the forward end of the housing  10 , the flange  30  comes up against the front end of the recess  32 . The flange  30  and front end of the recess  32  act as cooperating stop means which, via the plate  22 , restrain the centre section  18   a  of the staple back against further forward movement. Thus, as the actuator  16  continues to advance, the actuator arms  28  bend the outer sections  18   b  of the back of the staple forwardly through 90° to bring the free ends of the staple legs  20  towards one another and deform the staple into a generally rectangular closed shape,  FIG. 2(   c ). 
     At this point the base  36  of the recess  34  in the front of the actuator  16  is abutting against the centre section  18   a  of the staple base. Now, since the plate  22  remains restrained by engagement of the stop means  30 / 32  further forward movement of the actuator  16  will rupture the tabs  24  thus freeing the staple from the plate  22 . At this point the cycle is complete. 
       FIG. 5  shows an alternative embodiment for the staple. It comprises a standard round wire staple  40  having a rearwardly extending restraining plate  22  with upstanding flange  30  attached to the centre section of the staple back by rupturable tabs  24 . The tabs may be attached to the staple back by soldering, braising, laser welding, adhesive bonding, etc. The preferred process will ensure a consistent break-off force between the tabs and the staple back. 
     Referring now to  FIG. 6 , another embodiment of the staple is shown which includes two staples  14  disposed spaced apart one above and each having a respective rearwardly-extending restraining plate  22  joined thereto by rupturable tabs as previously described. In this case the rear ends of the parallel plates are joined by a common flange  30 . In such a case the stapling device would be modified such that stop means on the housing  10  projected into the space between the upper and lower plates  22  and engaged the flange  30  between them to restrain the back of the staple. The double staple could be driven by two actuators  16 , one disposed above the upper plate  22  and the other below the lower plate  22 , or a single actuator could be used having upper and lower branches which embrace the plates  22  between them. 
       FIG. 7  shows another staple usable in the invention in which the centre section  18   a  of the staple back is enlarged, for example by forming it as a disk  42 , so that the centre section  18   a  has a much greater area in a plane normal to the longitudinal axis of the housing  10  than either of the outer section  18   b.  This configuration has particular application in the field of vascular puncture closure. The process of closing puncture holes using conventional staples may be enhanced using this method as the disk  42  on the staple back provides greater surface coverage of the puncture hole area thereby effecting haemostasis in a shorter time. 
       FIG. 8  shows a configuration which is essentially the double staple as described in  FIG. 6  but for use in combination with a stapling device having a locator tube  44 . The locator tube  44 , which passes between the plates  22  through a hole (not shown) in the flange  30 , is slidable axially within the housing  10  between a forward position wherein it projects beyond the free forward end of the housing  10  to enter a puncture site in a liquid-carrying vessel in a human or animal, thereby to locate the free end of the housing at the puncture site, and a rearward position wherein the locator tube is retracted into the housing. In use a guidewire (not shown) extends within the locator tube and emerges from the forward end of the tube, the tube  44  being tracked along the guidewire to the puncture site and the guidewire and tube being retracted into the housing prior to closure of the staples. A locator tube is described in the aforementioned Irish Patent Application S2000/0722, and it will be clear to one skilled in the art how to modify the embodiment shown in  FIG. 2  to incorporate such a tube. This configuration has particular relevance in the area of vascular puncture closure. 
     The staple configurations shown in  FIGS. 6 to 8  are, like the staple shown in  FIG. 1 , designed so that they are easily manufactured as integral structures from sheet metal using a conventional metal stamping and bending processes. 
     The embodiment of staple shown in  FIG. 9  comprises a staple essentially as described with reference to  FIG. 7  but without the attached plate  22 . Instead, a rearwardly extending filament  46  is attached to the rear surface of the disk  42 . In use, the stapling device is adapted to trap or hold the rear end of the filament  46  so that it becomes taut at the point where the staple back is level with the front end of the housing  10  so that further advance of the actuator will bend the outer sections  18   b  of the staple back to close the staple as previously described. At this point the actuator may advance further forward thereby shearing or detaching the filament from the back surface of the disk  42 . Alternatively, the actuator may retract while simultaneously the device releases the filament at its rear end and consequently releasing the staple from the device. Examples of the filament material are Dacron, PLA, PGA and PLGA. 
     In  FIG. 10  a staple configuration is shown similar to that in  FIG. 3  except that the rupture tabs  24  are replaced with a slotted tab  50  which engages with an upstanding flange  52  integral to plate  22 . As the former advances forward to form the staple the back is held in position by the plate  22 . Once forming is complete the former component retracts while simultaneously causing the plate  22  to move down disengaging the flange  52  from the staple slot  50  allowing it to separate from the stapler device. 
       FIGS. 11 and 12  illustrate further embodiments of this principle. In  FIG. 11  the flange  52  engages a band  54  which is formed integrally with an lies parallel to the back  18  of the staple. In  FIG. 12  a pair of L-shaped cylindrical arms engage a channel section  58  of the staple back  18  to restrain the staple during forming. When forming is complete the former retracts while simultaneously causing the arms  56  to be pushed outwards, away from one another and out of engagement with the channel section  58 . 
     The invention is not limited to the embodiments described herein and may be modified or varied without departing from the scope of the invention.