Abstract:
A surgical access device comprises a seal assembly ( 51 ) having a plurality of part circular sealing members ( 55 ) each attached to a common ring ( 53 ) which is held within the device about its longitudinal axis. In use, the sealing members are located radially inwards of the ring in a stacked relationship. When not within the device, the sealing members are movable from a position radially outwards of the ring to a position radially inwards of the ring. A seal core comprises the seal assembly and a protective member which, in use, is located on the proximal side of the seal assembly. A method of assembling the surgical access device is also provided.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to surgical access devices and particularly, though not exclusively, to such devices for use in laparoscopy. 
       BACKGROUND TO THE INVENTION 
       [0002]    Laparoscopic ports facilitate access to the abdominal cavity during endoscopic or minimally invasive surgery. Laparoscopic entry devices require seals to prevent or minimise leakage of insufflation gas through the port when surgical instruments are inserted. 
         [0003]    During minimally invasive abdominal surgery, the patient is insufflated with carbon dioxide in order to create space between internal organs and other bodily tissue and thereby create a usable workspace for the surgeon to undertake a given procedure. For this reason a critical feature of any laparoscopic port access system is to ensure that no insufflation gas leaks through the port when instruments of varying sizes are inserted. 
         [0004]    During use, the port is first used to puncture the abdominal wall to create an access point through which the surgeon gains access to the abdominal cavity. This puncture is achieved via a component of the port assembly known as the trocar or obturator. The trocar or obturator is then subsequently removed from the assembly leaving the cannula in place, protruding through the abdominal wall of the patient. The patient can then be insufflated, with the cannula remaining in place, to provide the surgeon with an access point to the surgical site—the abdominal cavity. The cannula is the part of the port assembly which contains the seals. 
         [0005]    The insufflation gas is prevented from leaking through the cannula due to the presence of a non-return valve within the device. There are several types of non-return valve that can be employed within a cannula body to facilitate this, including flap valves, duckbill valves and quad type valves. 
         [0006]    When a surgical instrument is inserted through the port assembly, the non-return valve is forced open. A further seal assembly is therefore required, capable of conforming to the diameter of surgical instruments, to maintain insufflation pressure when the non-return valve is open. 
         [0007]    When a surgical instrument is removed from the port assembly, the non-return valve automatically closes, thus preventing leakage of the insufflation gas through the port assembly. 
         [0008]    The further seal assembly is a critical aspect a laparoscopic port system. The most basic seal employed to achieve the required functionality is a simple lip seal. This is typically a single piece elastomeric component, consisting of an outside diameter designed to fit inside the cannula housing, and an inside diameter designed to seal around the outside diameter of a surgical instrument. The disadvantage of this form of seal is that it is only designed to seal around one specific diameter of instrument. Therefore, if differing diameter instruments need to be used then more than one port needs to be inserted. To combat this problem, ports using simple lip seals need to incorporate several seals of different diameters which can be manually selected by the user. 
         [0009]    One such way this has been achieved is described in GB2441113 which discloses a port system with 3 simple lip seals of different diameters which can be manually selected via pivots on the cannula body. Although a configuration such as this does allow the device to be used with instruments of different diameters, it is undesirable that the user has to manually switch between seals when using multiple instruments of different diameters. 
         [0010]    To overcome this requirement for manual seal selection, efforts have been undertaken to develop an improved single or universal seal assembly, capable of automatically conforming to a range of different diameters. 
         [0011]    The first universal seal for a port system was described in U.S. Pat. No. 5,395,342 which discloses a seal with a simple conical elastomeric component with a hole at the apex. This elastomeric cone is assembled over a plurality of resilient legs extending inwardly from the inside diameter of the cannula housing. 
         [0012]    When an instrument is inserted through the cannula, the distal tip of the instrument firstly makes contact with the resilient legs. The resilient legs are then forced outwards, causing the hole in the apex of the elastomeric cone to dilate to the size of the instrument diameter. 
         [0013]    A disadvantage of this solution is the force required to insert a large diameter instrument through the assembly. The user typically desires to feel as little resistance as possible when inserting an instrument through a cannula. This high resistance is due to the fact that a single elastomeric component is being required to expand from below 5 mm diameter to above 12 mm diameter. 
         [0014]    Another disadvantage is the high level of friction between the instrument shaft diameter and the seal assembly. 
         [0015]    To overcome these problems, seal assemblies comprising a plurality of elastomeric components have been developed. 
         [0016]    One such arrangement is set out in US2007185453. In this embodiment, four individual elastomeric leaf components are interwoven at equal angular spacing to form the seal assembly. 
         [0017]    This arrangement is advantageous as the overlapping structure requires less force to dilate or expand to accommodate instruments of larger diameters. Another advantage of this design is that under expansion, each individual leaf component is subject to less tension, making the seal less vulnerable to damage from surgical instruments. 
         [0018]    A significant disadvantage of this design is that additional components, namely, the individual leaves have to be made. Furthermore, the intricacy of the assembly process adds cost and complexity to the manufacturing process. 
       Statements of the Invention 
       [0019]    According to the present invention, there is provided a surgical access device comprising a seal assembly comprising a plurality of part circular sealing members each attached to a common ring which is held within the device about its longitudinal axis and with the sealing members being located radially inwards of the ring in a stacked relationship, the sealing members being movable, when not within the device, from a position radially outwards of the ring to a position radially inwards of the ring 
         [0020]    Accordingly, the sealing assembly of the invention allows an otherwise complex multi-component assembly to be moulded as a single item. 
         [0021]    Preferably, the seal assembly comprises a single sheet of flexible material which may be arranged in a single plane with the part circular sealing members in a non-overlapping relationship. 
         [0022]    The seal assembly is such that the sealing members extend inwardly in a radial arrangement from an outer integral support ring which, when assembled with corresponding housing components, overlap one another to form a substantially planar surface that has a thickness greater than the individual seal members and has an aperture located at its centre. This facilitates an overlapping formation to be achieved from a single component rather than the intricate assembly of multiple components. 
         [0023]    The design of the seal assembly is such that the assembly of the sealing members means that their orientation changes to one another by a predetermined angle about the axis of the cannula such that the orifice is reduced when in an assembled state. 
         [0024]    The outermost surfaces of the sealing members become the innermost surface of the component when in their assembled state. This makes the sealing member viable for manufacture via standard injection or compression moulding techniques. 
         [0025]    The individual sealing members may be tapered (inclined rather than perpendicular) at their straight edges. This gives an improved airtight seal during use and also reduces friction between the seal member and a surgical instrument shaft. 
         [0026]    The individual sealing members are semi-circular in shape. This means that, when assembled, the seal assembly forms a circular footprint when viewed from above. This is preferable for the embodiment of the design into a laparoscopic port system. 
         [0027]    The sealing members may include a plurality of orifices adjacent their curved edges to assist in the clamping of the seal in its assembled state. The upper or lower housing may include integral posts to engage in the plurality of orifices. 
         [0028]    Preferably, the outer perimeter of the flattened semi-circular seal members are clamped between upper and lower housing components to retain the flattened arrangement during use. This is to ensure that the seal component retains the desired assembled state and does not revert back to its moulded state. 
         [0029]    The vertically protruding members may be profiled and dimensioned in such a way that allows them to engage with their mating surface. This is to facilitate a neater arrangement upon assembly. 
         [0030]    Preferably, the seal assembly is held within the device by a connection allowing the seal assembly to float relative to the remainder of the device. More preferably, the connection is formed from a flexible elastomeric ring of serpentine configuration. 
         [0031]    A flotation device connected to the primary sealing member allows axial movement of small diameter surgical instruments to be absorbed and thereby maintain the airtight seal between the shaft of the surgical instrument and the inner aperture of the sealing member. 
         [0032]    The connection may be integral with the seal assembly. 
         [0033]    Preferably, the device includes a protective member located adjacent and above (on the proximal side) the primary sealing member, the protective member contacting, in use, said sealing members. The protective member allows the inwardly distal ends of the protective member to contact the innermost diameter of the sealing assembly during use. This is to protect the sealing assembly from potential damage caused by traumatic surgical instruments. 
         [0034]    Preferably, the protective member comprises two components, one being located above and rotationally offset from the other. Each component may be in the form of a ring provided with two or more inwardly extending flexible leaves or flaps which allow an instrument to pass through the ring. Preferably, each component is provided with two diametrically opposed flaps. 
         [0035]    Preferably, the device is provided with a sealing arrangement axially and distally spaced from said sealing assembly. This sealing arrangement may be a one-way valve such as a duck bill valve. This sealing arrangement provides an airtight seal when no surgical instrument is present. 
         [0036]    The present invention further provides a seal core for a surgical access device of the invention, the seal core comprising at least the seal assembly and the protective member as described above. 
         [0037]    The present invention also provides a method of assembling a surgical access device having a seal assembly comprising a plurality of part circumferential sealing members each connected to a common support ring, the support ring being held within the device about its longitudinal axis, the sealing members being movable, when not within the device, from a position radially outwards of the ring to a position radially inwards of the ring, the method comprising the step of moving the sealing members from a position radially outwards of the ring to a position radially inwards of the ring, so that said sealing members are in a stacked relationship. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0038]    The accompanying drawings are as follows: 
           [0039]      FIG. 1  is a perspective view of the full port assembly of a surgical access device of the invention; 
           [0040]      FIG. 2  is a perspective view of the seal housing of the device of  FIG. 1 ; 
           [0041]      FIG. 3  is a perspective view of the device of  FIG. 1  in conjunction with a trocar assembly prior to instrument insertion therethrough; 
           [0042]      FIG. 4  is an exploded perspective view of the device of  FIG. 1  showing the constituent parts of the device; 
           [0043]      FIG. 5A  is a perspective view of the upper clamp of the device of  FIG. 1 ; 
           [0044]      FIG. 5B  is a sectional view of the upper clamp of  FIG. 5A ; 
           [0045]      FIG. 6  is a sectional view of the seal assembly of the device of  FIG. 1 ; 
           [0046]      FIG. 7  is a sectional view of the seal assembly of the device of  FIG. 1  and in conjunction with a 5 mm surgical instrument; 
           [0047]      FIG. 8  is a sectional view of the seal assembly of the device of  FIG. 1  and in conjunction with a 12 mm surgical instrument; 
           [0048]      FIG. 9  is a perspective view of the instrument seal of the device of  FIG. 1  showing the seal petals in their open (unfolded) state; 
           [0049]      FIG. 10A to 10E  show successive stages in the folding of the petals of the seal of  FIG. 9  into their closed positions; 
           [0050]      FIG. 11A  shows the protection or armour layer of the device of  FIG. 1  with its leaves in the open position; 
           [0051]      FIG. 11B  shows the protection or armour layer of the device of  FIG. 1  with its leaves in the closed position; 
           [0052]      FIG. 12  is a sectional view of one of the leaves of the protection layer of  FIG. 11A ; 
           [0053]      FIG. 13  is a part sectional view showing the insertion of a 12 mm surgical instrument through the protection layer and seal member of the device of  FIG. 1 ; 
           [0054]      FIG. 14  is a perspective view of the seal core of the assembly of  FIG. 1 ; and 
           [0055]      FIG. 15  is a top plan view of the seal core of  FIG. 14 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0056]    The present invention will now be described, by way of example only, with reference to the accompanying drawings. 
         [0057]      FIG. 1  shows a port assembly  1  consisting of an elongated tube  2  for inserting the port into the abdomen, a cannula body  3 , a gas tap  4  and a single use seal assembly  5 . The cannula body  3  and seal assembly  5  are commonly connected to one another permanently or detachably thereby aiding production of the parts and also giving the potential for the same cannula to be used with multiple seal assemblies. 
         [0058]      FIG. 2  shows the seal unit detached from the tube  2 . At its upper surface the unit is provided with a slot or recess  6  which enables an instrument such as an optical trocar provided with a corresponding protrusion to engage with the seal unit to maintain a desired rotational alignment between the instrument and the seal unit. 
         [0059]      FIG. 3  illustrates the port assembly  1  in conjunction with a trocar  7  which, in use, is pushed though the cannula and seal assembly  1 . When inserted, shaft  9  of trocar  7  extends down through elongate tube  2  until the underside  11  of trocar  13  mates against the upper surface  15  of cannula body  3 . At this point the trocar tip  17  extends out of elongate tube  2  by a predetermined amount. 
         [0060]    Referring to  FIG. 4 , seal assembly  1  includes the elongate (or cannula sheath) tube  2  to which the seal housing  19  is attached via face seal or gasket  21 . Gasket  21  is provided with a circumferentially and outwardly extending lip  23  which engages with a corresponding recess in the inner wall of seal housing  19 . 
         [0061]    The attachment between cannula sheath tube  2  and seal housing  19  is of the bayonet type, inner circumferentially spaced projections (not shown) on the seal housing  19  engaging in slots  25  of cannula sheath tube  2 . The seal housing  19  can be first pushed down on the cannula sheath tube  2  with the projections moving along axially extending portions of the slots  25 . 
         [0062]    Gas tap  4  includes a tap body  27 , which is integral with the seal housing  19 , and a lever  29  which carries an integral stop member  31 . Stop member  31  engages with features located within tap body  27  to limit the range of movement of lever  29 . This assists the surgeon by indicating when the tap is in its fully open or fully closed condition. 
         [0063]    Duck bill valve  33 , having an upper circumferential lip  35 , seats on a corresponding circumferential ledge located within seal housing  19 . 
         [0064]    An intermediate plate  37  locates within seal housing  19  above valve  33 . It provides a support surface  39  for the seal and also provides a lip  41  on which the bellows member (to be mentioned below) is mounted. 
         [0065]    Located on intermediate plate  37  is lower clamp  43  which is in the form of a flat ring  45  having extending axially from one surface a series of integral pegs  47  which are equally spaced apart. These pegs  47  are all of similar shape and size, being circular in cross section, apart from one peg  49  which is key shaped in cross section. 
         [0066]    Instrument seal member  51  is made from a thin flexible plastics material and includes central, flat ring  53  to which six part-circular petals  55  are integrally connected. As shown in  FIG. 4 , the seal member  51  is a planar member although, as will be described below, the petals can be folded over for use within the seal unit. 
         [0067]    Ring  53  has located therein equally spaced apart holes  57 , all of which are circular apart from one which is keyhole shaped. Ring  53  is for location on lower clamp  43  with pegs  47  of lower clamp  43  extending through corresponding holes  57  of ring  53 , as best seen in  FIG. 9 . 
         [0068]    Each petal  55  has a part circular edge  59  and a straight edge  61 . The petals  55  are equally spaced apart about ring  53  to which each petal  55  is connected by a living hinge which is indicated at  63  located at the part circular edge of the petal close to one end of the straight edge. Each petal  55  is provided with a plurality of holes  65  which are equally spaced apart and extend circumferentially and spaced inwardly from the part circular edge of the petal. As is best seen in  FIG. 9 , most of the holes  65  are circular. However, three of the petals  55  have keyhole shaped holes  67  and they are located at different positions in their respective petals for a reason that will be made clear below. 
         [0069]    Located above seal member  51  is a protection or armour layer  69  which is made of flexible plastics material. As best seen in  FIGS. 11A and 11B , armour layer  69  comprises two substantially circular elements  71  and  73  interconnected at their peripheral edges by an integral living hinge  75 . Both elements  71  and  73  are formed of resilient plastics which is more robust than that of seal member  51 . When located within the seal housing  19 , element  71  lies below element  73 . 
         [0070]    The protective or armour layer  69  may, instead of being a single piece, alternatively be formed of two separate elements corresponding to elements  71  and  73  shown in  FIG. 11A . 
         [0071]    Circular element  71  comprises an outer ring area  77  in which are located a series of equally spaced apart holes  79 , which are circular except for one keyhole shaped hole  81  and which are for location over the pegs  47  of lower clamp  43 . Within ring area  77  are located two flaps  83  each of which is broadly semicircular in shape with a gently curved edge  85  extending between the rounded ends of a peripheral edge  87  which extends slightly inwardly and parallel to ring area  77 . The gently curved edges of the two flaps  83  face each other on either side of a line passing through the centre of circular element  71 , the space between the opposite edges  85  decreasing from a relatively wide spacing at the centre of element  71  to narrower spacings at the radially outer positions. Each flap  83  is connected at its peripheral edge  87  to the ring area  77  by two spaced apart integral links  89 . This arrangement is such that the flaps  83  can be resiliently flexed out of the plane of the ring area  77 . 
         [0072]    Circular element  73  is of similar configuration to that of element  71  but with its two flaps  91  being aligned at 90° to the flaps  83  of element  71 . Each flap  91  has, adjacent its gently curved edge a strip  93  which has steeply reducing thickness from the body of the flap towards its free edge. The flaps  83  of element  71  have similar edge portions which do not appear in  FIG. 11A  but can be seen at  95  in  FIG. 11B  when the two circular elements  71 ,  73  are superimposed. These edge portions  93 ,  95  allow the edges of the flaps to be compliant to accommodate variations in the profile of the shaft of a surgical instrument especially when the instrument is being retracted. 
         [0073]      FIG. 13  illustrates the positions of both petals  51  and flaps  83  and  91  (shown as one item in  FIG. 13 ) during retraction of an instrument  96  from the seal assembly. 
         [0074]    Located above armour layer  69  is upper clamp  97  which functions to hinder the inversion of armour layer  69 . As best seen in  FIGS. 5A and 5B , upper clamp  97  is a ring having an axial wall  99  extending between an upper, outwardly extending flange  101  and a relatively wider lower, outwardly extending flange  103 . Flange  103  is provided with equally spaced apart hexagonal holes  105  to enable the upper clamp to be located on the pegs  47 . 
         [0075]    Extending inwardly from axial wall  99  of clamp  97  are two diametrically opposed flats or ledges  100  which assist in preventing the armour layer inverting on withdrawal of an instrument from the seal assembly. Each ledge  100  has a radial lower surface and a gently and smoothly inclined upper surface  102  , the latter facilitating the smooth entry of an instrument into the seal assembly. 
         [0076]    A flotation or bellows element  107  is located alongside upper clamp  97 . As best seen in  FIGS. 6, 7 and 8 , flotation element  107  is a ring of flexible elastomeric material which has a central portion  109  of serpentine configuration. The outer edge of the central portion  109  is provided with an enlarged head portion  111  which enables the flotation element  107  to be trapped between intermediate plate  37  and seal housing cap  113 . The inner edge of the central portion  109  is provided with a thickened tail portion which enables the flotation element to be fitted at this edge between the flanges  101  and  103  of upper clamp  97 . Flotation element  107  allows an instrument inserted into to seal assembly to have a considerable degree of orbital movement (radial float) without loss of the gas pressure during an operation. 
         [0077]    The cannula  3  is assembled for use in the following manner. The stopcock lever  29  is inserted in the stopcock body  29 . The gasket  21  is inserted. The valve  33  is introduced into the housing  19 . The intermediate plate is then positioned on top of the valve. 
         [0078]    Next the instrument seal member  51  is folded onto the lower clamp  43 . This process is illustrated in  FIGS. 9 and 10A to 10E .  FIG. 9  shows the initial positioning of the seal member  51  on the lower clamp  69  with the petals in their unfolded positions.  FIG. 10A  shows the position after one petal  115  has been folded over so that the holes  65  locate on certain of the pegs  47 . Then, previously adjacent petal  117  is folded over to reach the position illustrated in  FIG. 10B  and this is followed by the successive folding over of petals  119 ,  121  and  123 , as illustrated in  FIGS. 10C to 10E . Finally, petal  125  is folded over so that all petals are located on the pegs  47 . This is achieved by folding each petal, after the first petal, over the previously folded over petals and not by interleaving any petal with previously folded over petals. The result is a simple stacking of petals and this procedure avoids the need for a relatively difficult process of manoeuvring one or more petals to produce a woven configuration. 
         [0079]    Each petal is in effect moved radially with respect to the lower clamp and this requires that three of the petals  115 ,  117  and  119  each have a keyhole shaped hole which is located in a different position on the three petals so that the radial movement causes the keyhole shaped holes all to locate on key shaped peg  49  of lower clamp  43 . 
         [0080]    Referring to  FIGS. 4, 14 and 15  of the accompanying drawings, items  43 ,  51 ,  69 ,  97  and  107  together comprise a unit which is the seal core for the overall assembly. This unit may be used in other configurations of surgical access devices.