Cannula sealing

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.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a U.S. National Phase Application under 35 U.S.C. § 371 of International Patent Application No. PCT/GB2016/050057, filed Jan. 11, 2016, and claims the priority of GB1500328.8, filed Jan. 9, 2015, all of which are incorporated by reference in their entireties. The International Application was published on Jul. 14, 2016 as International Publication No. WO 2016/110720 A1.

FIELD OF THE INVENTION

The invention relates to surgical access devices and particularly, though not exclusively, to such devices for use in laparoscopy.

BACKGROUND TO THE INVENTION

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Another disadvantage is the high level of friction between the instrument shaft diameter and the seal assembly.

To overcome these problems, seal assemblies comprising a plurality of elastomeric components have been developed.

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.

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.

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

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

Accordingly, the sealing assembly of the invention allows an otherwise complex multi-component assembly to be moulded as a single item.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

The connection may be integral with the seal assembly.

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.

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.

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.

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.

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.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described, by way of example only, with reference to the accompanying drawings.

FIG. 1shows a port assembly1consisting of an elongated tube2for inserting the port into the abdomen, a cannula body3, a gas tap4and a single use seal assembly5. The cannula body3and seal assembly5are 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.

FIG. 2shows the seal unit detached from the tube2. At its upper surface the unit is provided with a slot or recess6which 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.

FIG. 3illustrates the port assembly1in conjunction with a trocar7which, in use, is pushed though the cannula and seal assembly1. When inserted, shaft9of trocar7extends down through elongate tube2until the underside11of trocar13mates against the upper surface15of cannula body3. At this point the trocar tip17extends out of elongate tube2by a predetermined amount.

Referring toFIG. 4, seal assembly1includes the elongate (or cannula sheath) tube2to which the seal housing19is attached via face seal or gasket21. Gasket21is provided with a circumferentially and outwardly extending lip23which engages with a corresponding recess in the inner wall of seal housing19.

The attachment between cannula sheath tube2and seal housing19is of the bayonet type, inner circumferentially spaced projections (not shown) on the seal housing19engaging in slots25of cannula sheath tube2. The seal housing19can be first pushed down on the cannula sheath tube2with the projections moving along axially extending portions of the slots25.

Gas tap4includes a tap body27, which is integral with the seal housing19, and a lever29which carries an integral stop member31. Stop member31engages with features located within tap body27to limit the range of movement of lever29. This assists the surgeon by indicating when the tap is in its fully open or fully closed condition.

Duck bill valve33, having an upper circumferential lip35, seats on a corresponding circumferential ledge located within seal housing19.

An intermediate plate37locates within seal housing19above valve33. It provides a support surface39for the seal and also provides a lip41on which the bellows member (to be mentioned below) is mounted.

Located on intermediate plate37is lower clamp43which is in the form of a flat ring45having extending axially from one surface a series of integral pegs47which are equally spaced apart. These pegs47are all of similar shape and size, being circular in cross section, apart from one peg49which is key shaped in cross section.

Instrument seal member51is made from a thin flexible plastics material and includes central, flat ring53to which six part-circular petals55are integrally connected. As shown inFIG. 4, the seal member51is a planar member although, as will be described below, the petals can be folded over for use within the seal unit.

Ring53has located therein equally spaced apart holes57, all of which are circular apart from one which is keyhole shaped. Ring53is for location on lower clamp43with pegs47of lower clamp43extending through corresponding holes57of ring53.

Each petal55has a part circular edge59and a straight edge61. The petals55are equally spaced apart about ring53to which each petal55is connected by a living hinge which is indicated at63located at the part circular edge of the petal close to one end of the straight edge. Each petal55is provided with a plurality of holes65which are equally spaced apart and extend circumferentially and spaced inwardly from the part circular edge of the petal. Most of the holes65are circular. However, three of the petals55have keyhole shaped holes67and they are located at different positions in their respective petals for a reason that will be made clear below.

Located above seal member51is a protection or armour layer69which is made of flexible plastics material. As best seen inFIGS. 10A and 10B, armour layer69comprises two substantially circular elements71and73interconnected at their peripheral edges by an integral living hinge75. Both elements71and73are formed of resilient plastics which is more robust than that of seal member51. When located within the seal housing19, element71lies below element73.

The protective or armour layer69may, instead of being a single piece, alternatively be formed of two separate elements corresponding to elements71and73shown inFIG. 10A.

Circular element71comprises an outer ring area77in which are located a series of equally spaced apart holes79, which are circular except for one keyhole shaped hole81and which are for location over the pegs47of lower clamp43. Within ring area77are located two flaps83each of which is broadly semicircular in shape with a gently curved edge85extending between the rounded ends of a peripheral edge87which extends slightly inwardly and parallel to ring area77. The gently curved edges of the two flaps83face each other on either side of a line passing through the centre of circular element71, the space between the opposite edges85decreasing from a relatively wide spacing at the centre of element71to narrower spacings at the radially outer positions. Each flap83is connected at its peripheral edge87to the ring area77by two spaced apart integral links89. This arrangement is such that the flaps83can be resiliently flexed out of the plane of the ring area77.

Circular element73is of similar configuration to that of element71but with its two flaps91being aligned at 90° to the flaps83of element71. Each flap91has, adjacent its gently curved edge a strip93which has steeply reducing thickness from the body of the flap towards its free edge. The flaps83of element71have similar edge portions which do not appear inFIG. 10Abut can be seen at95inFIG. 10Bwhen the two circular elements71,73are superimposed. These edge portions93,95allow 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.

FIG. 12illustrates the positions of both petals51and flaps83and91(shown as one item inFIG. 12) during retraction of an instrument96from the seal assembly.

Located above armour layer69is upper clamp97which functions to hinder the inversion of armour layer69. As best seen inFIGS. 5A and 5B, upper clamp97is a ring having an axial wall99extending between an upper, outwardly extending flange101and a relatively wider lower, outwardly extending flange103. Flange103is provided with equally spaced apart hexagonal holes105to enable the upper clamp to be located on the pegs47.

Extending inwardly from axial wall99of clamp97are two diametrically opposed flats or ledges100which assist in preventing the armour layer inverting on withdrawal of an instrument from the seal assembly. Each ledge100has a radial lower surface and a gently and smoothly inclined upper surface102, the latter facilitating the smooth entry of an instrument into the seal assembly.

A flotation or bellows element107is located alongside upper clamp97. As best seen inFIGS. 6, 7 and 8, flotation element107is a ring of flexible elastomeric material which has a central portion109of serpentine configuration. The outer edge of the central portion109is provided with an enlarged head portion111which enables the flotation element107to be trapped between intermediate plate37and seal housing cap113. The inner edge of the central portion109is provided with a thickened tail portion115which enables the flotation element to be fitted at this edge between the flanges101and103of upper clamp97. Flotation element107allows an instrument inserted into to the seal assembly to have a considerable degree of orbital movement (radial float) without loss of the gas pressure during an operation.

The cannula3is assembled for use in the following manner. The stopcock lever29is inserted in the stopcock body29. The gasket21is inserted. The valve33is introduced into the housing19. The intermediate plate is then positioned on top of the valve.

Next the instrument seal member51is folded onto the lower clamp43. This process is illustrated inFIGS. 9A to 9E.FIG. 9Ashows the position after one petal116has been folded over so that the holes65locate on certain of the pegs47. Then, previously adjacent petal117is folded over to reach the position illustrated inFIG. 9Band this is followed by the successive folding over of petals119,121and123, as illustrated inFIGS. 9C to 9E. Finally, petal125is folded over so that all petals are located on the pegs47. 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.

Each petal is in effect moved radially with respect to the lower clamp and this requires that three of the petals115,117and119each 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 peg49of lower clamp43.

Referring toFIGS. 4, 13 and 14of the accompanying drawings, items43,51,69,97and107together comprise a unit which is the seal core for the overall assembly. This unit may be used in other configurations of surgical access devices.