Patent Publication Number: US-6981966-B2

Title: Valve assembly for introducing instruments into body cavities

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation of application Ser. No. 08/814,757, filed Mar. 7, 1997 now U.S. Pat. No. 6,569,120, which is a continuation-in-part of application Ser. No. 07/873,416, filed Apr. 24, 1992 ABN and application Ser. No. 07/781,063, filed Oct. 18, 1991 now U.S. Pat. No. 5,203,773, the disclosures of which are hereby incorporated by reference herein. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to valve systems of the type adapted to allow the introduction of a surgical instrument into a patient&#39;s body. In particular, the invention is applicable to a cannula assembly wherein a cannula housing includes the valve assembly and the cannula is intended for insertion into a patient&#39;s body to sealingly accommodate an instrument inserted through the cannula and valve. 
   2. Background of the Prior Art 
   In laparoscopic procedures surgery is performed in the interior of the abdomen through a small incision; in endoscopic procedures surgery is performed in any hollow viscus of the body through narrow tubes or cannula inserted through a small entrance incision in the skin. Laparoscopic and endoscopic procedures generally require that any instrumentation inserted into the body be sealed, i.e. provisions must be made to ensure that gases do not enter or exit the body through the incision as, for example, in surgical procedures in which the surgical region is isufflated. Moreover, laparoscopic and endoscopic procedures often require the surgeon to act on organs, tissues, and vessels far removed from the incision, thereby requiring that any instruments used in such procedures be relatively long and narrow. 
   For such procedures, the introduction of a tube into certain anatomical cavities such as the abdominal cavity is usually accomplished by use of a trocar assembly comprised of a cannula assembly and an obturator. The cannula assembly includes a cannula tube attached to a valve assembly which is adapted to maintain a seal across the opening of the cannula assembly. Since the cannula tube is in direct communication with the internal portion of the valve assembly, insertion of the cannula tube into an opening in the patient&#39;s body so as to reach the inner abdominal cavity must maintain a relatively gas-tight interface between the abdominal cavity and the outside atmosphere. 
   Since surgical procedures in the abdominal cavity of the body require insufflating gases to raise the cavity wall away from vital organs, the procedure is usually initiated by use of a Verres needle through which a gas such as CO 2  is introduced into the body cavity. Thereafter, the pointed obturator of the trocar assembly is inserted into the cannula assembly and used to puncture the abdominal cavity wall. The gas provides a slight pressure which raises the inner wall surface away from the vital organs thereby avoiding unnecessary contact with the organs by the instruments inserted into the cannula. Following removal of the obturator, laparoscopic or endoscopic surgical instruments may then be inserted through the cannula assembly to perform surgery within the abdominal cavity. 
   In view of the need to prevent leakage of the insufflation gas from the cavity, the cannula is typically provided with a valve assembly which permits introduction of surgical instruments to provide selective communication between the inner atmosphere of the cavity with the outside atmosphere. In this regard, there have been a number of attempts in the prior art to provide such a seal as part of the cannula assembly. 
   One form of cannula valve assembly includes a flapper valve which is pivotally mounted within the cannula assembly and is automatically opened by the obturator or other object when it is inserted into the proximal end of the cannula. Conventional flapper valves may also be manually opened by pivoting a lever on the exterior of the housing. See, e.g., U.S. Pat. No. 4,943,280 to Lander. Trumpet valves are also known. 
   Other conventional cannula valve devices for accommodating surgical instruments include a single or plurality of flexible sealing members as shown, for example, in U.S. Pat. No. 4,655,752 to Honkanen et al., U.S. Pat. No. 4,909,798 to Fleischhacker, U.S. Pat. No. 4,673,393 to Suzuki et al., U.S. Pat. No. 4,610,665 to Matsumoto et al., and U.S. Pat. No. 4,869,717 to Adair. 
   Further, typical hemostasis valve devices are shown, for example, in U.S. Pat. No. 5,041,095 to Littrell, and U.S. Pat. No. 5,000,745 to Guest et al., 
   While attempts have been made to provide a valve assembly which maintains the integrity of the seal between the body cavity and the atmosphere outside the patient&#39;s body. Seal systems provided to date have failed to address the full range of surgeons&#39; needs, especially when instruments varying in diameter are used. Specifically, sealing elements currently used may be damaged when an instrument, such as a pointed obturator is passed therethrough. Moreover, present seal systems have not provided adequate sealing about an instrument before and after an instrument is passed therethrough. Also, existing seal systems have failed to provide adequate sealing of a cannula, or a trocar assembly having a cannula which accommodates instruments of varying diameters. It is a further disadvantage of existing seal systems that adequate sealing is not provided in conjunction with a structure for holding a cannula in a desirable position in an incision with respect to a patient&#39;s body. 
   It would therefore be desirable to provide a valve assembly which addresses these shortcomings in the art by maintaining a substantially fluid tight seal between an internal portion of a patient&#39;s body and the outside atmosphere during insertion and manipulation of a surgical instrument into the patient&#39;s body. Such an assembly may further provide stabilization or lateral limitation of motion of an instrument passed therethrough. Also, the valve assembly may inhibit fluids from exiting with the instrument while being withdrawn, and the valve assembly may inhibit contact with sealing structure. It is further desirable to provide a valve assembly for use with a cannula or trocar assembly which provides substantial fluid and gas tight sealing before and after an instrument is passed therethrough. It would also be desirable to provide a cannula which maintains a predetermined position of a cannula or trocar assembly in an incision. 
   The present invention provides a valve assembly which may be incorporated into a cannula assembly or utilized in combination with any type of tubular member for providing access into the body of a patient while permitting introduction of instruments through the valve assembly into the body. The valve assembly includes a sealing gasket which provides a desirable seal about an instrument inserted through the valve assembly. The valve assembly may further provide stabilization of the cannula or limit lateral motion of the cannula when an instrument is passed therethrough. Also, the valve assembly may include more than one sealing element providing improved sealing qualities under varied conditions. At all times, the surgeon maintains control over the interface between the atmospheres within and without the patient&#39;s body. Moreover, the present invention makes it possible to introduce instruments of varying sizes into the body and insures the maintenance of a gas seal despite instrument manipulation therethrough. 
   SUMMARY OF THE INVENTION 
   A valve assembly is provided for permitting the introduction of a surgical instrument into a patient&#39;s body through a tube such as a cannula. The valve assembly includes at least one sealing gasket constructed of a flexible material and having a passageway. The passageway is substantially closed prior to insertion of an instrument through the valve assembly forming a substantial gas tight seal. When an instrument is inserted through the passageway of the valve assembly the flexible material defining the passageway resiliently engages an outer surface of the instrument in a substantially gas tight manner. 
   The sealing gasket may include sealing structure having first and second overlapping elements. The sealing gasket can be removably positioned on a frame or in a housing assembly such that the first and second overlapping elements are tensioned. 
   The valve assembly may further include sealing structure comprising a third element having a substantially central aperture. The third element may have a tapered portion and be constructed at least partially of a flexible material. The third element accommodates an instrument passed through its central aperture providing substantial sealing about the instrument passed therethrough. A retainer structure inhibits contact by the instrument with adjacent sealing structure such as, the first and second elements of the gasket assembly or the third element. The retainer structure includes at least one movable portion and a substantially central aperture for accommodating the instrument. 
   The valve assembly may further provide a sealing structure comprising a fourth element for substantially removing fluids from the surface of an instrument passed therethrough. The fourth element may include a substantially central aperture defined by a deformable material such that the central aperture is capable of accommodating the instrument. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing features of the present invention will become more readily apparent and will be understood by referring to the following detailed description of preferred embodiments of the invention, which are described hereinbelow with reference to the drawings wherein: 
       FIG. 1  is an exploded perspective view of a cannula assembly illustrating a valve assembly according to the present invention; 
       FIG. 2  is a perspective view illustrating a sealing gasket assembly shown as part of the valve assembly illustrated in  FIG. 1 ; 
       FIG. 3  is a cross-sectional view of the sealing gasket assembly taken along line  3 — 3 ; 
       FIG. 4  is a perspective view of the sealing gasket assembly during the insertion of an instrument; 
       FIG. 5  is an exploded perspective view of a cannula assembly illustrating the valve assembly according to another embodiment of the present invention; 
       FIG. 6  is a front elevational view illustrating a rectangular retainer and a circular retainer in a coupled configuration; 
       FIG. 7  is an exploded perspective view illustrating the rectangular retainer and the circular retainer during the insertion of an instrument; 
       FIG. 8  is a front elevational view of a foam block shown as part of the valve assembly illustrated in  FIG. 5 ; and 
       FIG. 9  is an exploded perspective view of a cannula assembly illustrating the valve assembly according to another embodiment of the present invention. 
       FIG. 10  is an exploded perspective view illustrating a cannula and valve assembly according to the present invention; 
       FIG. 11  is an exploded perspective view illustrating a housing assembly of the valve assembly shown in  FIG. 10 ; 
       FIGS. 12 ,  13  and  14  are exploded perspective views of a cannula assembly illustrating the valve assembly of  FIG. 10  during the insertion of an instrument; 
       FIG. 15  is an exploded perspective view illustrating a valve assembly according to another embodiment of the present invention; 
       FIG. 16  is an exploded perspective view of a cannula assembly illustrating the valve assembly of  FIG. 15  during the withdrawal of an instrument; 
       FIG. 17  is an exploded perspective view illustrating a cannula and valve assembly according to another embodiment of the present invention; and 
       FIGS. 18 ,  19  and  20  are exploded perspective views illustrating the cannula and valve assembly of  FIG. 17  during the insertion of an instrument. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The present invention contemplates introduction into a patient&#39;s body of all types of surgical instruments including, but not limited to clip appliers, lasers, photographic devices, graspers, scissors, tubes, and the like. All of such objects are referred to herein as “instruments”. 
   Referring to the drawings, in which like reference numerals identify identical or similar elements, FIGS.  1 — 3  illustrate a preferred embodiment of a valve assembly  10 . The valve assembly  10  is incorporated into a cannula valve housing  12  having an upper half  12   a  and a lower half  12   b  attached at the proximal end of the cannula  14 . The valve assembly  10  provides a substantial seal between a body cavity of a patient and the outside atmosphere before and after an instrument is inserted through the cannula valve housing  12 . Moreover, each of the valve assemblies of the present invention is capable of accommodating instruments of varying diameters, e.g., from 3 mm to 15 mm, by providing a gas tight seal with each instrument when inserted, and returning to a fully sealed configuration upon removal of the instrument in the valve assembly. This flexibility of the present valve assembly greatly facilitates endoscopic surgery where a variety of instruments having differing diameters are often needed during a single surgical procedure. 
   Referring to  FIG. 1 , the valve assembly  10  includes a first retainer  16  at its proximal end and a second retainer  18  distal to the first retainer  16  and proximal a bellows seal  20 . The retainers  16 ,  18  are preferably formed of a suitable synthetic resin or plastic, such as polypropylene. The first and second retainers  16 ,  18  are essentially identical and both preferably include generally rectangular plates  22  having integrally molded circular body portions  24  extending orthogonally from the rectangular plates  22 . The body portion  16  mates with the proximal side of the sealing gasket assembly  36 . 
   Although the plates  22  are generally rectangular shaped in the preferred embodiments described herein and shown in the accompanying drawings, any plate shape may be desirable, such as, for example circular shaped. Further, other geometric configurations of the body portion  24  may be contemplated or, for example, the body portion  24  itself may be eliminated by attaching the movable portions  26  (described below) to the plate  22 . 
   As best seen in  FIG. 6 , preferably a plurality of triangularly shaped movable portions  26  are divided by a series of slits  28  and are attached to the perimeter  30  of the body portions  24  of the retainers  16 ,  18  by hinge regions  32 . The slits  28  extend radially outward from central aperture  34  of the retainers  16 ,  18 . 
   A sealing gasket assembly  36  is distal to the first retainer  16  and preferably includes identical first and second elements  38 ,  40  made of a flexible resilient material. Preferably, both the first and second elements  38 ,  40  include a substantially circular body  42  having a wall  44  defining a semi-circular opening  46 . As shown in  FIG. 3 , the outer perimeter of the body includes a groove  48  defined by two ridges  50 . The groove on the outer perimeter defines a ridge  52  on the inner circumference of the body  42 . 
   Although the sealing gasket assembly includes a substantially circular body as described in the preferred embodiments herein and illustrated in the accompanying drawings, the sealing gasket assembly may include a body having a different geometric configuration, such as, for example, a rectangular shape. Additionally, although sealing gasket assembly  36  is described in the preferred embodiments herein as consisting of first and second elements  38 ,  40 , it is also contemplated that first element  38  may have a semicircular wall of similar configuration to wall  40  bonded to the circumference of first element  38  to create two overlapping members. This approach eliminates one structure from the overall valve assembly. 
   As shown in  FIGS. 1 and 2 , the first and second elements  38 ,  40  cooperate by positioning the semi-circular opening  46  in each element radially opposite each other. Thus, the second element  40  fits over the first element  38  in overlapping relation such that the wall  44  of the first element  38  covers the opening  46  in the second element  40 , and the wall  44  of the second element  40  covers the opening  46  of the first element  38 . Further, the ridge  52  on the inner circumference of the second element  40  mates with the groove  48  in the first element  38 . The sealing gasket assembly  36  provides a substantially fluid tight seal before instrument insertion. 
   The flexible material allows the sealing gasket assembly  36  to accommodate instruments of varying sizes, e.g., diameters of from 3 mm to 15 mm. The sealing gasket assembly is preferably made of a flexible material having a durometer in the range of 25-35, and most preferably a durometer of 30. As shown in  FIG. 4 , flexible resilient walls accommodate an instrument  37  by resiliently deforming to enable the instrument  37  to pass therethrough. Upon removal of instrument  37 , sealing gasket assembly  36  returns to its initial position, thereby reestablishing a substantially fluid tight seal. To facilitate and ensure that the fluid tight seal is reestablished upon instrument removal, it is preferred that walls  44  be placed under tension, thereby creating a tautness which further biases walls  44  toward their initial overlapping, abutting relation. This tension may be created by molding elements  38  and  40  of a slightly smaller diameter than the matable portion of retainer  16 , and then stretching elements  38  and  40  to mate therewith. 
   The bellows seal  20  is positioned distally adjacent the second retainer  18  and is made of a suitable flexible resilient material. The bellows seal  20  is preferably formed of an elastomeric material such as, preferably, natural rubber. The bellows seal  20  has a generally circular body  54  and includes a circumferential ridge  56  positioned at its distal end. The ridge  56  defines the perimeter  58  of a recessed portion  60  having a substantially central aperture  62 . 
   The bellows seal  20  is adapted to accommodate an instrument through its central aperture  62 . The flexible material enables the aperture  62  to accommodate instruments of varying sizes while providing a substantially fluid and gas tight seal about the instrument, e.g., instruments having diameters of from 3 to 15 mm. The size of the aperture in the bellow seal is preferably from 2.5 mm to 3.0 mm (0.10 inches to 0.12 inches). The material of the bellows seal preferably has a durometer value in the range of 35 to 45, and most preferably a durometer value of 40. 
   When accommodating an instrument through the aperture  62  of the bellows seal  20 , the ridge  56  allows the recessed portion  60  surrounding the aperture  62  to accommodate the instrument while substantially encouraging the retention of the circular shape of the aperture. Further, the ridge  56  substantially reduces the chances, for example, of sealing integrity being compromised by instrument manipulation, or of the bellows seal material tearing. The bellows seal  20  as described in the preferred embodiments herein and illustrated in the accompanying drawings, could be any deformable sealing element which includes, for example, a different geometric aperture configuration. 
   In operation, referring to  FIGS. 1 and 4 , the first retainer  16  guides the instrument as it is being inserted through the valve assembly  10 . The first and second retainers  16 ,  18  encourage the instrument through the valve assembly by assisting the adjacent sealing gasket assembly  36  and the bellows seal  20  to accommodate the instrument. The triangular portions  26  of the retainers  16 ,  18  displace the flexible resilient material of the adjacent sealing gasket assembly  36  and bellows seal  20  encouraging easier access for the instrument. 
   Further, the triangular movable portions  26  of the retainers  16 ,  18  discourage unwanted contact between the instrument, such as a trocar obturator having a sharp tip, and the sealing gasket assembly  36  and the bellows seal  20  by, for example, providing an intermediate surface between the sharp instrument being inserted into the valve assembly  10  and the adjacent sealing gasket assembly  36  and bellows seal  20 . Both retainers provide support to the valve assembly such that manipulation of the instrument will not deter the instrument from the desired passageway, or compromise the valve assembly&#39;s sealing effect. 
   Although the gasket seal assembly is proximal the bellows seal as described herein and shown in the accompanying drawing of the preferred embodiments, the order may be reversed as desired. 
   Another embodiment of the valve assembly is shown in FIG.  5 . The valve assembly  10   a  is similar to the previous embodiment shown in  FIG. 1 , however, the embodiment shown in  FIG. 5  includes, in addition to other elements contributing to the sealing function of the valve assembly, a stabilizer plate  64  at its proximal end. The stabilizer plate  64  has a substantially central circular aperture  66  therethrough to accommodate a surgical instrument. An integrally molded lip portion  68  extends outwardly from the plane of the stabilizer plate further defining the aperture. The stabilizer plate  64  provides rigidity to the overall valve assembly  10   a , and further guides the instrument through a desired passageway in the valve assembly  10   a.    
   A first rectangular retainer  16  is distally adjacent to the stabilizer plate  64 . The first rectangular retainer  16  includes a circular body portion  24  which fits over the lip portion  68  of the stabilizer plate  64  and preferably frictionally engages lip portion  68 . The first rectangular retainer  16  is essentially identical to, and functions as described in the previous embodiment shown in  FIG. 1 ; however, in the present embodiment the first rectangular retainer  16  communicates with a first circular retainer  70 . 
   Referring to  FIG. 7 , the first circular retainer  70  includes a proximal and a distal ridge  72 ,  74  positioned about the perimeter and defining a groove  73  therebetween. Similar to the first rectangular retainer  16 , the first circular retainer  70  includes a plurality of triangular portions  76  divided by a series of slits  78  which are connected to the distal ridge  74  by hinge regions  80 . The slits  78  extend radially from a substantially central aperture  82 , and the first circular retainer  70  is dimensioned to fit over and preferably frictionally engage the body portion  24  of the first rectangular retainer  16 . The first rectangular retainer  16  and the first circular retainer  70  are juxtapositioned such that the slits  78 ,  28  of one of the retainers transect the triangular portions  26 ,  76  of the other retainer. For example, the retainers may be juxtapositioned such that the slits  78  of the first circular retainer  70  overlappingly transect the triangular portions  26  of the first rectangular retainer  16 . 
   The sealing gasket assembly  36  is positioned distal to the retainers  16 ,  70  and is identical to the sealing gasket assembly  36  described in the previous embodiment illustrated in  FIGS. 1-4  and associates similarly with the retainer members. In the present embodiment, however, the sealing gasket assembly  36  is positioned proximal to a foam block  84 . 
   The foam block  84  includes a generally rectangular proximal face  86  and tapers generally outwardly from a longitudinal center line to a rectangular distal face  88 . The foam block  84  includes a circular region  90  in its distal end partially extending therethrough to an end wall  92 . The end wall  92  includes an aperture extending through the proximal face which is defined by three slits  91  converging at a center point  94 , and biased closed by the foam, as shown in FIG.  8 . When an instrument is passed through the aperture the foam accommodates the instrument. Further, the foam block  84  biases the sealing gasket assembly  36  in the closed position and encourages the sealing gasket assembly  36  to resiliently assume the closed position after an instrument has been removed. 
   A distal retainer  96  is generally circular and is positionable inside the aperture in the foam block  84 . The distal retainer  96  includes a circumferential ridge  98  and a flange  100  extending orthogonally to the plane of the distal retainer  96 . Similar to the first circular retainer  70 , the distal retainer  96  includes a plurality of triangular portions  102  attached about the perimeter of the retainer by hinge regions  104 . A plurality of slits  106  define the triangular portions  102  and the slits extend radially from a central aperture  108 . 
   A second stabilizer  110  is adjacent to the distal retainer  96  and tapers generally inwardly towards a longitudinal center line from its proximal end. The proximal end  112  of the second stabilizer mates with the distal retainer  96  and the distal end  114  of the second stabilizer mates with the second rectangular retainer  18  (described below). The second stabilizer  110  provides guidance to the instrument as it passes through the valve assembly. The first stabilizer plate  64  and the second stabilizer  110  align the instrument and generally provide support for the entire valve assembly  10   a.    
   A second rectangular retainer  18  and a second circular retainer  116  are positioned distal to the second stabilizer  110 . The second retainers  18 ,  116  are essentially identical to the first rectangular and circular retainers  16 ,  70 , are combined in an identical manner, and function similarly. 
   A bellows seal  20  is positioned distal to the second retainers  18 ,  116  and mates with the second circular retainer  116 . The bellows seal  20  is identical to the bellows seal described in the previous embodiment illustrated in  FIG. 1 , and functions similarly. 
   In operation, referring to  FIG. 5 , a surgical instrument (not shown) may be inserted at the proximal end of the cannula housing  12 . The first and second rectangular retainers  16 ,  18 , the sealing gasket assembly  36 , and the bellows seal  20 , operate essentially the same as described in the previous embodiment illustrated in FIG.  1 . In the present embodiment, however, the stabilizer plate  64  receives the instrument and guides the instrument into the valve assembly  10   a . As shown in  FIG. 7 , as an instrument passes through the first and second rectangular and circular retainers  16 ,  70 ,  18 ,  116  the triangular plates  26 ,  76  pivot distally from a longitudinal center line of the retainers. As in the previous embodiment illustrated in  FIG. 1 , the retainers encourage the instrument through the sealing gasket assembly  36  and the bellows seal  20  by urging the flexible materials of the sealing gasket assembly and the bellows seal to accept the instrument. 
   Further, the rectangular and circular retainer combination  16 ,  70 ,  18 ,  116 , are juxtapositioned such that the slits of one retainer transect the triangular portions of the other, as shown in  FIGS. 6 and 7 . This overlapping arrangement more effectively discourages unwanted contact between the instrument and the other members of the valve assembly. For example, the retainers  16 ,  70 ,  18 ,  116  provide an interface between a pointed instrument being inserted into the valve assembly and the adjacent sealing gasket assembly or bellow seal, i.e., as the instrument projects into the slit  28  of the rectangular retainer  16 ,  18 , the circular retainer&#39;s triangular portions  76  extend between the instrument and the seal  36 ,  20 . 
   The instrument passes through the aperture of the foam block  84 , which is biased closed, through deformation and compression of the flexible resilient foam so as to accommodate the instrument. After the instrument is removed, the foam block  84  encourages the sealing gasket assembly  36  to return to its original position. 
   The distal retainer  96  is essentially identical to the first circular  70  and second circular retainers  116 . The distal retainer is designed to fit into the circular region  90  in the foam block. The distal retainer  96  operates as the retainers  16 ,  70  discussed above for discouraging unwanted contact between the instrument and the foam block  84 . 
   Another embodiment of the valve assembly positioned in a cannula housing  12  is shown in FIG.  9 . The valve assembly  10   b  is essentially the same as the previous valve assembly  10   a  shown in  FIG. 5 ; however, the embodiment illustrated in  FIG. 9  includes a foam member  118  having two portions  120 ,  122 , and two single element gasket seals  124  positioned distal to first retainers  16 ,  70  and distal to second retainers  18 ,  116 , respectively. 
   The two portions  120 ,  122  of the foam member  118  are in side-by-side abutting relation inside the cannula valve housing  12 . The two portions  120 ,  122  are biased towards each other by communicating with the walls of the cannula valve housing  12 . An instrument, however, may pass between the two portions  120 ,  122  of the foam member  118  by displacing the flexible resilient foam. 
   The two piece resilient foam member  118  biases the adjacent single element gasket seal  124  in a closed or rest position. After the withdrawal of an instrument, the foam member  118  urges the single element gasket seal  124  to return to its rest position. 
   Preferably, both the single element gasket seals  124  include a generally circular body  128  having a flange  130  at its proximal end extending radially outwardly. A central passageway  134  is biased closed by the resiliency of the material and is defined by three slits converging at a center point. As an instrument is passed through the aperture  134  defined by the three slits the resilient material accommodates the instrument. After the instrument has been removed the resilient material of the single element gasket seals  124  return to its original configuration. The single element gasket seal  124  proximal the foam member  118 , for example, may accommodate a partially inserted instrument while the distal single element gasket seal  124  remains in a closed or at rest position. 
   The first stabilizer plate  64 , the first and second rectangular retainers,  16 ,  18  and the circular retainers,  70 ,  116  are essentially the same as described in the previous embodiment illustrated in FIG.  5  and operates similarly. 
   The valve assembly described in the preferred embodiments and illustrated in the accompanying drawings is preferably capable of accommodating instruments varying in diameter from 3 mm to 15 mm, and most preferably diameters from 5 mm to 12 mm. When inserting the instrument into the valve assembly as described herein the insertion force, i.e., the axial force asserted against the instrument to pass the instrument into and through the valve assembly is preferably kept to a minimum. 
   For example, preferable insertion forces of approximately no more than 5 pounds are desirable for instruments having approximate diameters of more than 9 mm. Most preferably, insertion forces of approximately no more than 4 pounds are desirable for instruments having approximate diameters of between 5 mm and 8 mm. 
   Moreover, preferable insertion forces of approximately 7 pounds are desirable for instruments having approximate diameters of 9 mm to 15 mm. Most preferably, insertion forces of approximately no more than 6 pounds are desirable for instruments having approximate diameters of between 10 mm and 12 mm. 
   Referring to  FIGS. 10-20 , several embodiments of a valve assembly according to the present invention are illustrated. In each embodiment the valve assembly includes sealing structure having at least three elements which contribute to the sealing function of the assembly. The valve assembly is incorporated into a cannula valve housing  12  having an upper half  12   a  and a lower half  12   b  attached at the proximal end of the cannula  14  which is configured as an elongated tubular member, and also shown in  FIGS. 1 ,  5  and  9 . A tissue gripping apparatus  240  and a cannula member  254 , as shown in  FIGS. 10 and 17 , may be attached to the cannula  14 . The cannulas proximal end is closest to the surgeon and its distal end is opposite the proximal end. Both the distal and proximal ends of the cannula are referred to herein for reference. 
   The valve assemblies shown in  FIGS. 10-20  provide a substantial seal between a body cavity of a patient and the outside atmosphere before and after an instrument is inserted through the cannula valve housing  12 . Moreover, each of the embodiments of the valve assemblies are capable of accommodating instruments of varying diameters, e.g., from 3 mm to 15 mm, by providing a substantial gas and fluid tight seal before and after instrument insertion. This instrument accommodating flexibility of the present valve assemblies greatly facilitates endoscopic surgery where a variety of instruments having differing diameters are often needed during a single surgical procedure. 
   Referring to  FIGS. 10-14 , a preferred embodiment of a valve assembly  140  includes a two piece housing assembly  142 , sealing structure comprising a sealing gasket assembly  144  having first and second elements, and sealing structure further comprising a third sealing element embodied as a conical seal  148 , conical retainers  150 , square retainers  146 , a stabilizer plate  152 , and a fastening ring  154 . 
   The sealing gasket assembly  144  of the valve assembly  140  is positioned in the housing assembly  142 . The sealing gasket assembly  144  may include characteristics similar to sealing gasket assembly  36  described above and shown in  FIGS. 1-5 . 
   Specifically, the sealing gasket assembly  144  preferably includes identical first and second overlapping sealing elements  156 ,  158  made of a flexible resilient material. Preferably, both the first and second sealing elements  156 ,  158  include a circumferential ridge  160  and a wall  162  enclosed by the ridge  160 . Each wall  162  includes a semi-circular opening  164 . 
   Each of sealing elements  156 ,  158  includes a pair of radially opposed holes  166 , as best seen in FIG.  11 . The holes  166  mate with the pins  168  of the cylindrical body portion  170  of the two piece housing assembly  142 . Although the sealing gasket assembly  144  is shown being attached to the housing assembly  142  by pins  168 , other methods may be used, such as, for example, adhesives. 
   The flexible nature of the elements  160  of the sealing gasket assembly  144  enable the elements  160  to mate with one another by stretching one element  160  over the other. The elements  160  cooperate by positioning the semi-circular opening  164  in each element  160  radially opposite each other. Thus, the first and second sealing elements  160  mate in overlapping relation such that the wall  162  of one element overlaps the semi-circular opening  164  of the other element. 
   The overlapping sealing elements  160  define a sealable passageway therethrough. The flexible nature of the walls  162  allow the sealing gasket assembly  144  to deformably accommodate an instrument passed therethrough. Moreover, the walls  162  resiliently return to their original position after removal of an instrument. Thus, the overlapping relation of the elements of the sealing gasket assembly  144  provides a substantially fluid tight seal before instrument insertion and helps to discourage fluid passage around an instrument passed through the sealing gasket assembly  144 . 
   The sealing gasket shown  FIGS. 10-14 , as with the previous sealing gasket shown in  FIGS. 1-5 , includes flexibly resilient material allowing the sealing gasket assembly  36  to accommodate instruments of varying sizes, e.g., diameters of from 3 mm to 15 mm. The sealing gasket assembly  144  is preferably made of a flexible material having a durometer valve in the range of 25-35, and most preferably a durometer valve of 30. 
   To facilitate and ensure that the fluid tight seal is reestablished upon instrument removal, it is preferred that walls  162  of the elements  160  be placed under tension, thereby creating a tautness which further biases walls  162  toward their initial overlapping, abutting relation. 
   The tensioning of the overlapping sealing elements  160  further encourages the overlapping elements  160  to surround an instrument passed therethrough. The overlapping elements  160  are biased in an overlapping abutting relation to substantially discourage gas and fluid leakage through the valve assembly. When an instrument is inserted through the passageway, the flexible overlapping elements  160  accommodate and substantially surround the outer surface of the instrument. The flexible nature of the overlapping elements surround the instrument providing substantial gas and fluid sealing. 
   The tension is created in the walls  162  of the sealing gasket  144  by stretching each element  160  onto the pins  168  of the housing assembly  142 . Each hole  166  mates with the corresponding pin  168  of the housing assembly  142 . The pin  168  placement requires that the elements  160  be substantially stretched to mate the holes  166  with the pins  168 . This secures the elements to the cylindrical body portion of the housing assembly  142  while creating and maintaining the desired wall  162  tension. As shown in  FIG. 12 , flexible resilient walls accommodate an instrument  37  by resiliently deforming to enable the instrument  37  to pass therethrough. Fluid flow is discouraged around the instrument by the flexible elements  160  substantially surrounding the instrument  37  as it is passed therethrough. The tensioning of the overlapping elements  160  further provides radial tensioning of the overlapping elements  160  on the surface of the instrument. The contact between the overlapping elements  160  and the surface of the instrument helps to prevent the unwanted egress of fluids when an instrument  37  is passed through the valve assembly. 
   Upon removal of instrument  37 , resiliently deformable sealing gasket assembly  144  returns to its initial position, thereby reestablishing a substantially fluid tight seal with the instrument  37  removed. 
   The valve assembly  140  may also include structure for inhibiting unwanted contact between an instrument being inserted and sealing structure, in this case, the sealing gasket assembly  144 . A preferred embodiment of such structure is shown in  FIGS. 10-14  as first and second square retainers  146 . Although, the first and second retainers  146  are shown as square, other configurations are also contemplated, such as, circular. The retainers may be somewhat similar to the retainers  16  and  18  shown in FIG.  5  and described above. 
   Each of the square retainers  146  of the present embodiment shown in  FIGS. 10-14  are essentially identical to each other and include a body portion  171  having a series of triangularly shaped portions  172  defining a series of slits  174  therebetween. As best seen in  FIG. 11 , preferably, a plurality of triangularly shaped movable portions  172  are divided by a series of slits  174  and are attached to the body portion  171  by hinge-like regions  176 . The triangularly shaped portions  172  are positioned radially about a substantially central axis. The slits  174  of the one of the retainers  146  bisect the triangular portions  172  of the other retainer  146 . The square retainers  146  are preferably formed of a suitable synthetic resin or plastic, such as polypropylene. 
   The square retainers  146  are juxtapositioned such that the slits of one of the retainers transect the triangular portions  172  of the other retainer to provide enhanced protection of the sealing gasket assembly  144  from an instrument inserted into the valve assembly  140 . 
   As the instrument passes through the square retainers  146 , the triangular portions  172  accommodate the instrument by moving distally exposing the split  174  therebetween to the entering instrument. However, the adjacent sealing gasket assembly  144  remains uninjured by the entering instrument because the overlapping square retainers  146  distally positioned with respect to triangular portions  172  discourage the instrument from contacting the sealing gasket assembly  144 . Contact is discouraged because the square retainers  146  are positioned between the entering instrument and the sealing gasket assembly  144 , and the juxtapositioning of the square retainers  146  provide a substantially continuous surface protecting the sealing gasket assembly  144 . 
   The valve assembly  140  may also include structure for stabilizing the instrument when the instrument is passed through the valve assembly  140 . An embodiment of such structure in accordance with the present invention is shown in  FIGS. 10-14  as a stabilizer plate positioned proximally of the square retainer plates  146 . 
   The stabilizer plate  152  has some similarities to the stabilizer plate  64  shown in FIG.  5 . The stabilizer plate  152  shown in  FIGS. 10-14  is generally square in shape and includes a body portion  178  defining a substantially central circular aperture  180  therethrough to accommodate a surgical instrument. The stabilizer plate  64  provides rigidity to the overall valve assembly  140 , and further guides an instrument through a desired passageway in the valve assembly  140 . 
   The valve assembly  140  may also include sealing structure comprising a third sealing element for substantially sealing the valve assembly after an instrument is passed therethrough. An embodiment of such a third sealing element in accordance with the present invention is shown in FIGS.  10  and  12 - 14  as a conical seal  148  positioned distally adjacent to conical retainers  150  and constructed of a suitable flexible resilient material. 
   The conical seal  148  includes a body portion  182  having a tapered section  184  which has a substantially conical configuration and a substantially central hole  186  therethrough. The body portion  182  further includes a circumferential ridge  188  positioned proximal to the tapered section  184 . The ridge  188  is substantially integral with the body portion  182  and extends radially outwardly from the body portion  182 . 
   The conical seal  148  is preferably formed of an elastomeric material such as, for example, natural rubber. 
   The elastomeric material of the conical seal  148  allows the conical seal  148  to accommodate instruments of varying diameters through its central aperture  186 . The elastomeric tapered section  184  of the conical seal  148  deforms and flexes for sealing about the instrument passed therethrough. As the instrument is passed through the hole  186  of the tapered section  184 , the elastomeric material of the conical section deforms to accommodate the instrument, as shown in FIG.  14 . The deformation of the tapered section  184  is desirable for substantially sealing about the instrument. 
   The flexible material of the tapered section  184  enables the hole  186  to accommodate instruments of varying sizes while providing a substantially fluid and gas tight seal about the instrument, e.g., instruments having diameters of from 3 mm to 15 mm. The size of the hole  186  in the conical seal  148  is preferably from 2.5 mm to 3.0 mm (0.10 inches to 0.12 inches). The material of the conical seal  148  preferably has a durometer value in the range of 30 to 45, and most preferably a durometer value of 40. 
   The conical configuration, or frustoconical shape of the conical seal  148  favorably influences the amount of insertion force required to pass an instrument therethrough. The conical shape of the seal  148  deformably adapts to the inserted instrument, thus, reduced insertion forces on the instrument are required. 
   The valve assembly  140  may also include another embodiment of a structure for inhibiting unwanted contact between an instrument being inserted and sealing structure, in this case, the conical seal  148 . A preferred embodiment of such structure is shown in  FIGS. 10 , and  12 - 14 , as conical retainers  150  which are essentially identical. Each conical retainer  150  includes a body portion  190  having a tapered portion  192  being generally conically shaped. The tapered portion  192  includes a series of triangularly shaped sections  194  defining a series of slits  196  therebetween. The triangularly shaped sections  194  are positioned radially about a substantially central axis. The slits  196  of one conical retainer  150  bisect the triangular sections  194  of the other conical retainer  150 . The conical retainers  150  are preferably formed of a suitable synthetic resin or plastic, such as polypropylene. 
   As best seen in  FIG. 12 , preferably, a plurality of triangularly shaped movable portions  194  are divided by a series of slits  196  and are attached to the perimeter  198  of the conical retainers  150  by hinge regions  152 . The slits  196  extend radially outward from central aperture  200  of the conical retainers  150 . The conical retainers  150  are juxtapositioned such that the slits  196  of one of the retainers transect the triangular portions  194  of the other retainer, in a similar manner as with the square retainers  146 . 
   When an instrument is passed through conical retainers  150 , thereby entering the conical seal  148 , the triangular portions  194  discourage unwanted contact with the conical seal  148 . Contact is discouraged in a similar manner as with the square retainers  146  discussed above. 
   The housing assembly  142  of the valve assembly  140  shown in  FIGS. 10-14  is a preferred embodiment of a structure for tensioning overlapping first and second elements of the sealing gasket assembly  144 . The housing assembly  142  comprises a cylindrical body portion  170  having a passageway  204  therethrough. The cylindrical body portion  170  may act as a frame for receiving the sealing gasket assembly  144 . The housing assembly  142  further includes a housing end cap  208  removable positioned proximal to the cylindrical body portion  170 , and a fastening ring  154  positioned distal to the body portion  170 . The proximal end of the cylindrical body portion  170  of the housing assembly  142  includes outer and inner ridges  210 ,  212 , both extending proximally with respect to the cylindrical body portion  170 . The ridges  210 ,  212  define a groove  214  therebetween that is dimensioned and configured for mating with the sealing gasket assembly  144 . The ridge  210 ,  212  also includes a groove  216  circumscribing an inner surface of the outer ridge  210  which is also dimensioned and configured to receive the sealing gasket assembly  144 . 
   Further, two pins  168  extend proximally from the cylindrical body portion  170 . The two pin  168  are passed through the mating holes  166  in the sealing gasket assembly  144  to provide the desired tensioning of the gasket sealing assembly  144 , as well as, to fixedly position the sealing gasket  144  in the housing assembly  144 . 
   The end cap  218  of the housing assembly  142  includes inner and outer  220 ,  222  concentric ridges defining a groove  224  therebetween. The groove  224  is dimensioned and configured to receive the proximal end of the sealing gasket assembly  144 . Once the sealing gasket assembly  144  is seated therein, the housing end cap  218  can be mated with the cylindrical body portion  170  of the housing assembly  142 . The housing end cap  218  and the cylindrical body porion  170  of the housing assembly  142  can be mated, for example, by welding, or adhesive, or by other methods known in the art. 
   As best seen in  FIG. 11 , the end cap  218  of the housing assembly  142  further includes a proximally extending rectangular portion  226 . The rectangular portion  226  of the housing end cap  218  has a generally L-shaped inner portion having a proximally extending ridge  228 . The inner side of the rectangular portion  226  is dimensioned and configured to removable receive the square retainers  146  and the stabilizer plate  152  providing positive placement of the retainers  146  and stabilizing plate  152  therein. 
   The cylindrical portion  170  of the housing assembly  142  further includes at its distal end, concentric inner and outer flanges  230  and  232  defining a channel  234  therebetween. The channel  234  is dimensioned and configured to accommodate the conical retainers  150 , conical seal  148 , and the fastening ring  154  in mating relation. 
   The fastening ring  154  is positioned distal to the conical seal  148 . The fastening ring  154  includes a circular body portion  236  having an aperture  238  therethrough. The aperture  238  has an inner diameter dimensioned to fit over the tapered portion  184  of the conical seal  148  and abut ridge  188 . The fastening ring  154  mates with the channel  234  to hold the conical seal  148  and the conical retainers  150  in place. The fastening ring  154  may be attached to the housing assembly  142  by, for example, welding or adhesive, or by other methods known in the art. 
   It is envisioned that the conical sealing member  148  and the sealing gasket assembly  144  can be positioned proximal or distal to each other and be equally effective. 
   Referring to  FIGS. 10 and 17 , according to the present invention, a tissue gripping apparatus  240  is used with the elongated tubularly shaped cannula  14 . The tissue gripping apparatus  240  includes a cylindrical body portion  242 , and a flexible element  246  having a plurality of substantially parallel articulated arms  248 . Each of the arms  248  have a hinge  250  located proximal to a midpoint of each respective arm  248 , preferably each hinge  250  is substantially the same distance from the midpoint of the respective arms  248 . 
   The cylindrical body portion  242  may be constructed, preferably, of a substantially resilient flexible material such that the cylindrical body portion  242  can frictionally engage the elongated tubular cannula  14 . The frictional engagement of the cylindrical body portion  242  with the cannula  14  allows the body portion  242  to be slidable positionable along the canula  14 . The body portion  242  is moved distally to fully deploy the tissue gripping apparatus  240 ; that is, when the articulated arms  248  are in an extended position bending at their hinges  250 . 
   An actuation member  252  is situated at a proximal end of the cylindrical body portion  242 . The actuation member  252  allows a surgeon to easily move the cylindrical body portion  242  distally to deploy the articulated arms  248 . The articulated arms  248  are in a preferred deployed position when the arms  248  proximal the hinge  250  are in a substantially perpendicular orientation relative to the body portion  242 . This perpendicular orientation ensures optimum retention of the surgical apparatus in, for example, the abdomen by securingly engaging the inner wall of the abdominal cavity. other actuation systems whereby cylindrical body portion  242  may be moved distally to deploy arms  248  may, of course, be employed. 
   Referring to  FIGS. 10 and 17 , a cannula member  254  is provided for use with a tubular member, such as the cylindrical body portion  242  of the tissue gripping apparatus  240 , or a cannula or similar device to deter the escape of gases from the body cavity passed the cannula inserted therein and to provide support to the cannula inserted in the body cavity. For example, gasses may escape when a surgeon is engaging in endoscopic or laparoscopic procedures requiring insufflation of the body cavity or the cannula may undesirably slant making instrument insertion difficult. 
   An embodiment of a cannula member  254  for use with a cannula  24  and working in concert with the tissue gripping apparatus  240  is shown in  FIGS. 10 and 17 . The illustrated cylindrical cannula member  254  is slidably positioned about the body portion  242  of the tissue gripping apparatus  240 . The cannula member  254  includes a body portion  256  having concentric inner and outer flanges  258 ,  260 . The flange  258  and  260  are positionable against a patient&#39;s body to provide sealing and stabilizing properties. 
   The cannula member may be, for example, constructed of an elastomeric material, which is preferably an elastomer commercially available under the trademark “SANTOPRENE”, manufactured by Monsanto. 
   The cannula member  254  is contemplated to be rigid enough such that the flanges  258 ,  260  of the cannula member can be placed against a patients skin to enhance stabilization of the cannula  14  positioned through the body wall of the patient. The cannula&#39;s  14  increased stability provides greater ease of entry into the cannula  14  by the surgeon, as well as, moderating angular movement of the cannula  14 . This increased stability decreases the likelihood of irritation or trauma around the entry site of the cannula  14  into the body cavity. 
   Although the cannula member moderates angular movement of the cannula  24 , some angular movement of the cannula  24  is likely and may be desirable. Cannula member  254  is designed to remain in substantial contact with the patient&#39;s body while accommodating the cannula  14  in varying angular positions with respect to the patient&#39;s body. 
   In operation, the cannula member  254  as shown in  FIGS. 10 and 17  is used with the cannula  14  and in concert with the tissue gripping apparatus  240 . Typically, a trocar device including, for example, an obturator (not shown) and a cannula  14  is employed to puncture the skin and provide access to the surgical area. A pointed obturator may be used for penetrating the skin to extend the trocar beyond the body wall to the surgical site. Alternatively, an incision may be made using a scalpel or similar device before inserting a blunt obturator through the incision. When either obturator is removed, the cannula remains in place to maintain access to the surgical site, and several incisions may be made to provide numerous access ports to the surgical objective. 
   Once the cannula(s) are in place, the tissue gripping apparatus  240  is actuated into a deployed position by moving the actuation member  252  distally. The articulated parallel arms  248  move outwardly as hinges  250  extend the parallel arms  248  to a fully deployed position. The location of the hinge  250  on the articulated parallel arms  248  allows the portion of the arms  248  proximal the hinge  250  to be substantially perpendicular to the tubular portion  242  of the tissue gripping apparatus  240 . The cannula  14  is thereby secured in the incision by the extended articulated parallel arms  248  of the tissue gripping apparatus  240 . 
   The cannula member  254  is then urged towards the patient&#39;s body by manually advancing the cannula member  254  distally until the inner and outer flanges contact the patient&#39;s skin. The outer and inner  258 ,  260  contact the patient&#39;s skin providing a substantial gas seal flanges  258 ,  260  for maintaining insufflation pressure within the body cavity, and stabilizing the cannula  14  in the incision. 
   The cannula member  254  is designed to remain in substantial contact with a patient&#39;s body while accommodating the cannula  14  in varying angular positions with respect to a patient&#39;s body. More specifically, the cannula member  254  is at least partially constructed of flexible material which allows for angular juxtapositioning of the cannula  14  with respect to a patient&#39;s body while maintaining a substantial relationship between the flanges of the cannula member  254  and a patient&#39;s body. 
   The cannula member  254  has adequate rigidity for providing stabilization of the cannula  14 . The rigid nature of the cannula member  254  enhances support of the cannula  14  positioned through an incision in the body cavity. The cannula&#39;s  14  increased stability provides greater ease of entry into the cannula  14  by the surgeon, as well as, moderating angular movement of the cannula  14 . This increased stability decreases the likelihood of irritation or trauma around the entry cite of the cannula into the body cavity. 
   Referring to  FIGS. 12-14 , the valve assembly  140  operates as described below. A surgical instrument may be inserted at the proximal end of the cannula housing  12 . As the instrument  37  is passed through the valve assembly  140 , the stabilizer plate  152  receives the instrument  37  and guides the instrument  37  into the valve assembly  140 , as shown in FIG.  12 . 
   As an instrument  37  passes through the retainers  146  the triangular plates  172  pivot distally from a longitudinal center line of the retainers  146 . The overlapping retainers  146  encourage the instrument through the valve assembly  140  by assisting the sealing gasket assembly  144  to accommodate the instrument  37 . The triangular portions  172  of the retainers  146  displace the flexible resilient material of the adjacent sealing gasket assembly  144  encouraging easier access for the instrument  37 . 
   Further, the triangular movable portions  172  of the retainers  146  discourage unwanted contact between the instrument  37 , such as a trocar obturator having a sharp tip, and the sealing gasket assembly  144 . More specifically, the retainers  146  provide an intermediate surface between a sharp instrument being inserted into the valve assembly  40  and the adjacent sealing gasket assembly  140 . Both retainers also provide support to the valve assembly  140  such that manipulation of the instrument  37  will not deter the instrument from the desired passageway, or compromise the valve assembly&#39;s  140  sealing effect. 
   Further, the square retainers  146  are juxtapositioned such that the slits of one retainer  146  transect the triangular portions  172  of the other, as shown in FIG.  11 . This overlapping arrangement more effectively discourages unwanted contact between the instrument  37  and the other members of the valve assembly, in this case the sealing gasket assembly  144 . 
   Referring to  FIG. 12 , as the instrument  37  continues through the valve assembly  140  it enters the housing assembly  142  and engages the sealing gasket assembly  144 . The sealing gasket assembly  144  accommodates the instrument  37  in the operable passageway defined by the overlapping elements  160 . The overlapping elements  160  substantially surround the outer surface of the instrument  37  and discourage fluids and gasses from escaping from around the instrument  37 . 
   Referring to  FIGS. 13 and 14 , as the instrument  37  extends through the distal end of the housing assembly  142 , it engages the conical retainers  150  and the conical seal  148 . As with the square retainer  146  described above, the triangular portions  194  of the conical retainers  150  discourage unwanted contact with the conical seal  148 . Contact is discouraged because the conical retainers  150  are positioned between the entering instrument  37  and the conical seal  148 . 
   Further, similarly to the square retainers  146  described above, as an instrument  37  passes through the conical retainers  150  the triangular plates  194  pivot distally from a longitudinal center line of the retainers  150 . The overlapping retainers  150  encourage the instrument  37  through the conical seal  148  by assisting the conical seal  148  to accommodate the instrument  37 . The triangular portions  194  of the retainers  150  displace the flexible resilient material of the adjacent conical seal  148  encouraging easier access for the instrument  37 . 
   As the instrument  37  is passed through the central aperture  186  of the conical seal  148  the elastomeric material of the tapered section  184  deforms and flexes to accommodate the instrument  37 . The flexible nature of the conical seal  148  provides sealing about the instrument  37  passed therethrough. 
   After the surgery is completed, the surgical instrument  37  may be withdrawn from the cannula  14 . The valve assembly  140  provides substantial fluid and gas tight sealing before and after the instrument  37  is withdrawn. 
   To remove the cannula  14 , the cannula member  254  may first be manually moved proximally, or the cannula member  254  may also be moved proximally by releasing the tissue gripping apparatus  240 . By either method, the distal movement of the cannula member  254  removes the flanges  258 ,  260  from contact with the patient&#39;s skin. 
   The tissue gripping apparatus  240  may be removed by releasing the articulated parallel arms  248  of the tissue gripping apparatus  240 . The articulated parallel  248  arms are returned to their at rest position by moving the actuation member  252  proximally. 
   After the tissue gripping apparatus  240  is released, the entire tissue gripping apparatus  240 , and cannula  14  may be withdrawn from the incision. 
   Another embodiment of a valve assembly positioned in a cannula housing  12  is shown in  FIGS. 15 and 16 . The valve assembly  262  is essentially identical to the previous valve assembly  140  shown in  FIGS. 10-14 , however, the embodiment illustrated in  FIGS. 15 and 16  includes sealing structure having a fourth sealing element embodied as wiper means or spitback seal  264 . The similar elements between the embodiments shown in  FIGS. 10-14  and  FIGS. 15 and 16  function in a similar manner to the valve assembly  140  embodiment shown in  FIGS. 10-14  and described above. However, the spitback seal  264  of the embodiment shown in  FIGS. 15 and 16  includes characteristics as described below. 
   The spitback seal  264  is preferably positioned between a rectangular retainer  146  and a stabilizing plate  152 . The spitback seal  264  may also be positioned at other locations, such as, distal to the sealing gasket assembly  144 . 
   Typically, as the instrument  37  is removed from the valve assembly  262 , fluids may be on the surface of the instrument and are removed with the instrument  37 . These unwanted fluids can be disruptive to the surgeon. To substantially discourage such fluids from egressing from the valve assembly  262  in this manner, a spitback seal  264  is provided. 
   The spitback seal  264 , preferably, has a generally square shape, but may be other configurations, such as rectangular. The spitback seal  264  is constructed at least partially of a deformable material defining a substantially central aperture  266 . The substantially central aperture accommodates the instrument  37 , as seen in  FIG. 16 , such that the deformable material defining the aperture  266  contacts the outer surface of the instrument  37  substantially removing fluids therefrom. 
   More specifically, as the instrument  37  is withdrawn from the valve assembly  262 , the deformable material of the spitback seal  264  which defines the aperture  266  therethrough substantially engages the outer surface of the instrument  37 . The flexible nature of the spitback seal  264  may deform in a proximal direction as shown in FIG.  16 . This deformability substantially enables the material of the spitback seal  264  defining the aperture  266  to remove fluids clinging to the surface of the instrument  37  as the instrument  37  is removed from the valve assembly  262 . Thus, fluids are discouraged from exiting the valve assembly  262  as the instrument  37  is removed therefrom. 
   Another embodiment of a valve assembly  270  positioned in a cannula housing  12  is shown in  FIGS. 17-20 . The valve assembly  270  may include similarities to the previous valve assembly  140  shown in  FIGS. 10-14 . 
   Referring to  FIG. 17 , the valve assembly  270  includes stabilizer plate  152 , square retainers  146 , sealing gasket assembly  144 , and housing assembly  142 , which are essentially identical to those shown in  FIGS. 10-14  as part of valve assembly  140  described above. 
   The valve assembly  270  further includes first and second circular retainers  272  which are essentially identical. Each retainer  272  includes a body portion  274  having a plurality of movable triangular portions  276  movable attached to the body portion  274 . Both circular retainers  272  the plurality of triangular portions  276  divided by a series of slits  278 . The slits  278  extend radially from a substantially central aperture  280 . The circular retainers  272  are juxtapositioned such that the slits  278  of one of the retainers  272  transect the triangular portions  276  of the other retainer  272 . 
   The valve assembly  270  further includes sealing structure comprising a fifth sealing element embodied as a bellows seal  20  for substantially sealing the valve assembly after an instrument is passed therethrough. The bellows seal  20  is identical to the bellows seal  20  shown in  FIGS. 1 and 5 . The bellows seal  20 , shown in  FIGS. 17-20  is positioned distal to the retainers  272 . The bellows seal  20  mates with the circular retainer  272  in a similar manner as the bellows seal  20  mates with the second rectangular retainer  18  and second circular retainer  116  shown in FIG.  5 . 
   The bellows seal  20  and the circular retainers  272  are positioned in the channel  234  of the housing  142  in a similar manner as with the conical seal  148  and conical retainers  150  shown in  FIGS. 10-14 . Further the fastening ring  154  secures the bellows seal  20  and the circular retainers  272  in the housing assembly  142  in a similar manner as with the conical seal  148  and conical retainers  150  shown in  FIGS. 10-14 . 
   In operation, referring to  FIGS. 18 and 19 , as an instrument passes through the square retainers  146 , and the gasket seal  144  housed in the housing assembly  142 , the retainers  146  and the gasket seal  144  accommodate the instrument  37  in essentially the same manner as in valve assembly  140  described above and shown in  FIGS. 10-14 . 
   Referring to  FIG. 20 , the instrument engages the first and second circular retainers  272  and the bellows seal  20  in a manner which may be similar to the retainers  18 , and  116  and the bellows seal  20  shown in FIG.  5 . As shown in  FIG. 20 , the overlapping circular retainers  272  encourage the instrument  37  through the valve assembly  270  by assisting the bellows seal  20  to accommodate the instrument  37 . Further, the triangular movable portions  276  of the circular retainers  272  discourage unwanted contact between the instrument  37  and the sealing gasket assembly  144  and the bellows seal  20 . 
   While the invention has been particularly shown, and described with reference to the preferred embodiments, it will be understood by those skilled in the art that various modifications and changes in form and detail may be made therein without departing from the scope and spirit of the invention. Accordingly, modifications such as those suggested above, but not limited thereto, are to be considered within the scope of the invention.