GAS-TIGHT SEAL FOR SURGICAL TROCARS

Abstract: A gas-tight seal module (6) is incorporated in a trocar system to form a gas-tight seal about an instrument (12) inserted into the cannula of the trocar system. The module (6) incorporates an apertured disc (30). The aperture in the disc can be stretched to accommodate a seal about an instrument (12) inserted into the cannula. The disc is carried by a flaccid membrane (20) which extends across the module (6). A pair of rigid washers (32 and 34) clamped on opposite sides of the disc (6) are constrained for movement between two parallel spaced surfaces. The disc is thus freely moveable in its own plane to accommodate off-axis movement of the instrument so avoiding the breakage of the seal with the instrument which would otherwise occur if the disc did not have the same freedom of movement. The disc (30) also acts to clean the surface of the instrument when withdrawn so as to avoid contamination of a flap valve (10) upstream of the disc (30).

Description: GAS-TIGHT SEAL FOR SURGICAL TROCARS The present: invention relates to gas-tight seals and to trocar systems incorporating such seals. Trocar systems are used during abdominal operations for maintaining a passage through the abdominal wall of a patient. Trocar systems generally comprise a cannula in the form of an elongate tube terminating in an enlarged upper body and an obdurator or cutting tool which is fed through the enlarged upper body and down the elongate tube to pierce the abdominal wall so that the elongate tube can follow the tool through the wall. The cutting tool is then removed leaving the way clear for elongate surgical instruments or equipment, such as endoscopes, to be fed into the abdomen through the tube. To provide space within the abdomen, the abdomen is inflated with a gas and this allows easy access to the various organs located within the abdomen. To maintain gas pressure the trocar system is provided with a flap valve which is urged by the pressure of gas into a closed state. The flap valve has, however, to be opened to allow the passage of surgical tools therepast. Accordingly a sealing system is provided in the enlarged upper body to provide a seal around the surgical instrument once it has been inserted into the enlarged upper body. This now creates a gas lock between the flap valve and the seal and so the flap valve can now be opened (either by pushing the instrument against it or by other means) substantially without loss of pressure in the abdomen. The instrument can now be fed into the abdomen and manipulated as required. Usually more than one trocar is used so as to provide multiple entry points into the abdomen. The diameter of the instruments used is usually much smaller than the diameter of the tube or the enlarged body and so a considerable amount of lateral off-axis movement of the instruments can and does take place in order to effect: the desired manipulation of the instrument. Because the seals used are static any movement of the instrument other than axial is liable to strain the seal often to the extent of temporarily breaking the seal and so allowing gas to escape. Also most seals are designed v/ith a specific diameter of instrument in mind and so different seals or adaptors are required when changing instruments. It is an object of the invention to provide an improved seal. According to the present invention there is provided a trocar comprising an elongate tail portion for insertion through the abdominal wall of a patient and a head portion defining a compartment accommodating a replaceable seal module, the seal module comprising a housing containing a gas impermeable barrier extending across a chamber in said housing and secured to make a substantially gas-tight seal with the internal wall of the chamber, said barrier having a central elastic portion with an opening which can be stretched to accommodate the passage of elongate instruments of different cross-section to form a substantially gas-tight seal with such instruments, means for constraining said central portion in such a way as to allow displacement relative to the compartment in a predetermined plane, substantially without impediment. According to the present invention there is further provided a replaceable seal module for a trocar comprising a housing defining a chamber, a barrier extending across said chamber to make a substantially gas tight seal with the internal wall of the chamber, the barrier having a generally central elastic portion with an opening which can be stretched to accommodate the passage of elongate instruments of different cross-section to form a substantially gas tight seal with such instruments, means for constraining the central portion for displacement in plane substantially perpendicular to the axis of the opening, the outer portion of the barrier allowing displacement of the central portion substantially without resistance. A gas-tight seal embodying the present invention will now be described, by way of example with reference to the accompanying diagrammatic drawings in which: Figure 1 is a section through a trocar system down which a surgical instrument has been passed; Figure 2 is a fragmentary exploded view of the gas-tight seal module of the trocar system; Figure 3 is a section through the gas-tight seal module accommodating a surgical instrument; Figure 4 is the same section as in Figure 3 but with the surgical instrument laterally displaced; and Figure 5 is a plan view of a valve seal used in the module of Figure 2. The trocar system shown in Figure 1 comprises an elongate tube or tail 2 terminating in an enlarged head or upper body portion 4. The enlarged upper body portion 4 has a compartment which accommodates a removable seal module 6. The seal module 6 may be sealingly locked into the body portion 4 by a screw threaded cap 8. An elongate medical instrument 12 (for example the optical probe of an endoscope) passes through the seal module 6 and the tube 2. The seal module 6 is shown in more detail in Figure 3. The module 6 comprises a cylindrical body portion 14 defining a chamber which is open at one axial end and closed by an end wall 16 at the opposite axial end. The end wall 16 has a central circular opening 18. A barrier in the form of a membrane 20 extends across the inner chamber defined by the body portion 14. The membrane 20 has a flat outer circumferential portion 22 (see Figure 2) having an outer circumference substantially equal to the inner circumference of the body portion 14. A cylindrical clamping ring 24 is located within the chamber to urge the circumferential portion 22 against the inner face of the end wall 16. The membrane 20 has a central disc shaped portion 28 and an intermediate undulating portion 28 which allows the central disc shaped portion 26 to move freely within predetermined limits with respect to the outer circumferential portion. The membrane is of flaccid material, for example latex. The central disc shaped portion 28 is reinforced with a disc 30 of silicone material. The disc 30 is clamped to the disc shaped portion 28 with the aid of a pair of co-operating rigid washers 32 and 34. Pins 36 in the washer 32 pass through mating holes in the disc 30 and portion 26 to engage in a locking (push-fit) manner with corresponding holes 38 in the washer 34. The clamping ring 24 has a radially inwardly extending flange 40 which when the ring 24 clamps the portion 22 against the wall 16 forms with the wall 16 a space in which the sub-assembly of washers 32 and 34 has just sufficient clearance for sliding movement in the plane of the disc 30. The central portion 26 and the disc 30 are thus imprisoned or constrained for movement in two dimensions in their own planes. A locking member 42 is accommodated in the body portion 14 to urge the clamping ring into clamping engagement with the outer circumferential portion 22. The locking member 42 may be a push fit under a circumferential lip 44 at the open axial end of the body portion to lock the components of the module 6 together. In a modification other methods of locking the locking member in place may be used for example by using a circlip engaging a groove on the inner face of the body portion 14 - D - or by means of a screw thread on the locking member engaging a corresponding screw thread on the inner face of the body portion 14. The locking member has an annular collar 46. The internal diameter of the locking member 42 and the washers 32 and 34 are substantially equal to the diameter of the opening 18. The silicone disc 30 and the disc shaped portion 26 each have an aperture therein substantially smaller than the opening 18. For example the aperture may have a diameter, when the disc is unstressed, of less than a quarter of the diameter of the opening 18. The diameter of the aperture in the disc, when unstressed, should also be smaller than the diameter of the smallest instrument that is intended to be used with the seal. Because the disc is of silicone rubber the aperture can be stretched significantly beyond its original size by the insertion of larger diameter instruments. For example the diameter of the aperture could be more than doubled so as to accommodate different instruments having a diameter in the range of from 4 to 13mm. The locking member 42 has a circular recess which accommodates an elastic circular disc 10 of silicone rubber. The disc is imprisoned between the locking member 42 and the clamping ring 24 but allowed a very slight amount of play so that it can readily resume its original shape when released from being stressed. The disc 10 has a pair of centrally intersecting slits 10B (see Figure 5) which form four flaps 10A in the disc 10 which can be displaced by the pressure of the instrument 12. Normally the flaps 10A are closed and so they provide a valve which acts to prevent the escape of gas from the module. Instead of intersecting slits a single profiled cut can be made in the disc to form a displaceable flap for the instrument to displace and pass through. In operation the module 6 is locked into the enlarged upper portion of the body portion 4 of the trocar system using the cap 8. Upon the insertion of the instrument 12 the flaps 10A are displaced to allow the passage of the instrument 12 but will form a partial seal around the instrument 12. The instrument is then passed through the silicone disc 30 which will form a tight seal about the instrument. Upon withdrawal of the instrument 12 any debris drawn by the instrument from the abdominal area will be scraped off the instrument by the silicone disc 30 and so there is little or no danger of such debris being lodged in the slits of the disc 10 to prevent complete closure of the flaps upon withdrawal of the instrument. The complete closure of the flaps thus again prevents the escape of gas from the module. The instrument 12 can be displaced radially of the module 6 substantially without resistance because of the flaccid undulating portion 28 (see Figure 4) . The disc 30 is however constrained against angular displacement out of its plane by the washers 32 and 34. Instead of washers 32 and 34 being used to constrain the disc 30, axially extending projections on the axial end wall 16 and the flange 40 may be used to constrain the disc 30 for movement in its own plane. In this case the disc 30 may be welded or adhesively secured to the membrane 20. In yet another modification, the disc 30 may form an integral part of a composite membrane 20. It will be appreciated that the module 6 can be manufactured as a disposable module to be discarded after a single use. If the module is required to be reusable it can readily be removed from the trocar and autoclaved. Instead the module can be subject to Gamma or ethylene- oxide treatment.

Claims: CLAIMS 1. A trocar comprising an elongate tail portion for insertion through the abdominal wall of a patient and a head portion defining a compartment accommodating a replaceable seal module, the seal module comprising a housing containing a gas impermeable barrier extending across a chamber in said housing and secured to make a substantially gas-tight seal with the internal wall of the chamber, said barrier having a central elastic portion with an opening which can be stretched to accommodate the passage of elongate instruments of different cross-section to form a substantially gas-tight seal with such instruments, means for constraining said central portion in such a way as to allow displacement relative to the compartment in a predetermined plane, substantially without impediment. 2. A trocar according to Claim 1 wherein said constraining means comprises a pair of rigid annular rings matingly clamping said central portion between them and located between a pair of parallel facing surfaces which constrain said rings for slidable displacement in said predetermined plane. 3. A trocar according to Claim 1 wherein said central portion is semi-rigid and wherein said constraining means comprise guides located on opposite sides of the central portion in closely spaced proximity to said central portion. 4. A trocar according to any one of Claims 1 to 3 wherein said outer portion of said barrier is of latex. 5. A trocar according to any preceding claim wherein said central portion is of silicone rubber. 6. A trocar according to Claim 2 wherein said annular rings are of plastics. 7. A trocar according to any preceding claim wherein said housing is generally cylindrical, open at one axial end and closed at the opposite axial end except for a central opening substantially similar in size to said central portion, an annular clamping ring sized to be accommodated in said housing to urge the peripheral portion of said barrier against the closed axial end of the housing, a radially inwardly directed flange extending from said clamping ring and terminating in a central opening aligned with and having a size comparable with that of the central opening in said one axial end of said housing and a locking member for locking the clamping ring in the housing. 8. A seal according to Claim 7 wherein said locking member forms a snap fit with said housing. 9. A seal according to Claim 7 or to Claim 8 wherein said locking member includes an annular collar for guiding said elongate instruments towards the opening in said barrier. 10. A replaceable seal module for a trocar comprising a housing defining a chamber, a barrier extending across said chamber to make a substantially gas tight seal with the internal wall of the chamber, the barrier having a generally central elastic portion with an opening which can be stretched to accommodate the passage of elongate instruments of different cross-section to form a substantially gas tight seal with such instruments, means for constraining the central portion for displacement in plane substantially perpendicular to the axis of the opening, the outer portion of the barrier allowing displacement of the central portion substantially without resistance. 11. A module according to Claim 10 wherein the barrier extends across said chamber at a downstream end portion thereof and including a valve supported to extend across the chamber at an upstream end portion thereof, said valve being normally closed to prevent the escape of gas from said downstream end portion, but being openable to allow the passage of a said instrument therethrough. 12. A module according to Claim 11 wherein said valve comprises a laminar member of resilient material provided with a cut defining at least one flap which can be displaced by the passage of said instrument. 13. A module according to Claim 12 wherein said laminar member is provided with intersecting cuts which define a plurality of flaps.

Inventors: HOSKIN WILLIAM JOHN, KEMP NICHOLAS RICHARD, HOSKIN, WILLIAM, JOHN, KEMP, NICHOLAS, RICHARD
Applicants: HOSKIN WILLIAM JOHN, KEMP NICHOLAS RICHARD, MICROSURGICAL EQUIPMENT LTD, HOSKIN, WILLIAM, JOHN, KEMP, NICHOLAS, RICHARD, MICROSURGICAL EQUIPMENT LTD.
Application year: 1995
Main classification: A61B17
IPC codes: A61B17, A61M39