Patent Publication Number: US-2023157722-A1

Title: Natural orifice surgery system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 17/188,447 filed Mar. 1, 2021 entitled “Natural orifice system,” which is a continuation of U.S. patent application Ser. No. 16/204,902 filed Nov. 29, 2018 entitled “Natural orifice surgery system,” now U.S. Pat. No. 10,952,768, which is a continuation of U.S. patent application Ser. No. 14/826,336 filed Aug. 14, 2015 entitled “Natural orifice surgery system,” now U.S. Pat. No. 10,172,641, which claims the benefit of U.S. Provisional Patent Application Ser. No. 62/038,082, filed Aug. 15, 2014 entitled “Natural orifice surgery system,” the entire disclosures of which are incorporated by reference. 
    
    
     BACKGROUND 
     Technical Field 
     This application is generally directed to surgical devices, and more particularly, to an access device adapted for use with a cap, that is useful in natural orifice single-port surgical procedures and which is particularly useful in vaginal surgical procedures. 
     Description of the Related Art 
     Access devices are commonly used in surgery to facilitate the introduction of various surgical instruments into natural biological vessels, conduits, orifices, cavities, and other interior regions of the body. These access devices include, for example, devices that facilitate the introduction of a needle into a vessel, and trocars that facilitate the introduction of laparoscopic instruments into the abdomen of the body. 
     Some of these access devices are introduced into regions that include a fluid or gas under pressure. In the case of a needle access device, the pressure may be from a liquid, such as blood. In the case of a trocar, the pressure may be from a gas, such as an insufflation gas. In either case, it is desirable to provide for the introduction of the surgical instrument into the cavity without permitting the escape of the pressurized fluid or gas. 
     In the case of trocars, a cannula at the distal end of the trocar is typically connected to a seal housing at the proximal end of the trocar. Together the cannula and housing form a working channel through which various instruments can be inserted to access the cavity. Seal mechanisms are commonly disposed in the housing and include a septum valve that seals the working channel when an instrument is in place, and a zero closure valve that seals the working channel when the instrument is removed. 
     Current surgical access ports allow for single instrument access through each port, or allow for multiple instrument access through a rigid cannula. Some devices, such as transanal endoscopic microsurgery (TEMS) units require that the device be attached to the surgical table to support the weight of the device, as well as to locate the position of the device respective to the patient. These devices do not provide flexibility to the surgeon in selecting instrument size, and they restrict instrument movement with their rigid cannulas. Additionally, surgeons are performing laparoscopic surgical procedures through a single or a limited number of access ports. The procedures may be performed through a single two (2) centimeter incision at the umbilicus, or in certain cases, trans-vaginally or trans-anally. What is needed is a system that meets the needs of these new procedures, facilitating more flexible movement of laparoscopic instruments through a single or limited number of ports while preventing the escape of pressured fluids or gasses and permitting large specimen removal. What is particularly needed is an access system that can be deployed into a natural body cavity, such as the vagina, providing a sealed system for insufflation and a platform for the introduction of multiple surgical instruments of varying sizes, while maintaining sufficient stability for anchoring the system within the cavity without damaging the body cavity wall. 
     SUMMARY OF THE INVENTION 
     The invention is directed to a surgical access port system adapted for performing surgical procedures at a natural orifice comprising, an outer ring, wherein the outer ring is configured to be disposed proximate the natural orifice of the patient; a tubular body having a longitudinal axis, a proximal end and a distal end; a funnel segment extending between and coupling the outer ring and the proximal end of the tubular body, wherein the funnel segment provides a diametric reduction between the outer ring and the tubular body; and a flange disposed around the tubular body, the flange comprising a circular ridge circumscribing a channel, wherein the flange is adapted to secure the retractor within the body orifice. The flange may be disposed around the distal or the proximal end of the tubular body. 
     Optionally, the surgical access port system further comprises a removable gel cap, wherein the gel cap comprises a gel pad and a cap ring coupled with the gel pad, wherein the cap ring is engagable with the outer ring. 
     In another embodiment, the surgical access port system comprises an outer ring, wherein the outer ring is configured to be disposed proximate the natural orifice of the patient; a tubular body having a longitudinal axis, a proximal end and a distal end; a funnel segment extending between and coupling the outer ring and the proximal end of the tubular body, wherein the funnel segment provides a diametric reduction between the outer ring and the tubular body; and a frustoconical bolster disposed around the tubular body, the bolster comprising a first diameter at a distal end and a second diameter at a proximal end, the second diameter being larger than the first diameter, wherein the bolster is adapted to externally occlude the natural orifice. 
     In some embodiments, the bolster comprises at least one of a thermoset polymer and a thermoplastic elastomer. In some embodiments, the bolster is fixed around the proximal end of the tubular body. Optionally, the access system further comprises a flange disposed around the tubular body, distal to the bolster and/or an inflatable balloon disposed around the tubular body, distal to the bolster. In some embodiments, the bolster is slidably engaged with the tubular body. 
     In another embodiment, the surgical access port system comprises an outer ring, wherein the outer ring is configured to be disposed proximate the natural orifice of the patient; a tubular body having a longitudinal axis, a proximal end and a distal end; a funnel segment extending between and coupling the outer ring and the proximal end of the tubular body, wherein the funnel segment provides a diametric reduction between the outer ring and the tubular body; a mechanical balloon disposed around the tubular body, the mechanical balloon comprising a series of arms disposed along the longitudinal axis of the tubular body, each arm having a proximal end attached to a first ring and a distal end attached to a second ring, wherein the second ring is fixed to the tubular body; and a third ring disposed around the tubular body proximal to the first ring, the third ring adapted to move along the tubular body to engage the first ring and push the first ring toward the distal end of the tubular body, thereby placing a load on the arms and causing them to flare out from the tubular body. The mechanical balloon may also be used in combination with a compression flange or a bolster cone. 
     Optionally, the arms comprise a semi-rigid material. In some embodiments, each of the arms further comprises an articulating joint along the length of the arm. 
     In another embodiment, the surgical access port system comprises an outer ring, wherein the outer ring is configured to be disposed proximate the natural orifice of the patient; a tubular body having a longitudinal axis, a proximal end and a distal end; a funnel segment extending between and coupling the outer ring and the proximal end of the tubular body, wherein the funnel segment provides a diametric reduction between the outer ring and the tubular body; and an inflatable saddle-shaped balloon disposed around the tubular body, the saddle-shaped balloon comprising a first peak and a second peak, the second peak displaced from the first peak along the longitudinal axis of the tubular body. In some embodiments, the saddle-shaped balloon is adapted to compress the tissue of the natural orifice between the first peak and the second upon inflation to thereby occlude the natural orifice. 
     In another embodiment, the surgical access port system comprises an outer ring, wherein the outer ring is configured to be disposed proximate the natural orifice of the patient; a tubular body having an exterior surface, a longitudinal axis, a proximal end and a distal end; a funnel segment extending between and coupling the outer ring and the proximal end of the tubular body, wherein the funnel segment provides a diametric reduction between the outer ring and the tubular body; a retaining sleeve, the retaining sleeve comprising a longitudinal axis, a proximal end, a distal end, and a lumen, wherein the tubular body is disposed within the lumen and adapted to move along the longitudinal axis of the retaining sleeve; and at least two arms, each arm connected to the distal end of the retaining sleeve with an articulating hinge, wherein the arms are movable from a closed position to an open position as the distal end of the tubular body engages the arms. 
     Optionally, each arm further comprises an angled lead near the articulating hinge, the lead positioned to engage the distal end of the tubular body as the tubular body is moved through the retaining sleeve. In some embodiments, the access port further comprises an external thread wrapped around the exterior of the tubular body and an internal thread wrapped around an interior surface of the lumen of the retaining sleeve, wherein the external thread is adapted to engage the internal thread. In other embodiments, the access port further comprises a plurality of teeth disposed along the exterior surface of the tubular body and a plurality of pawls disposed along an interior surface of the lumen of the retaining sleeve, wherein the teeth are adapted to engage the pawls to facilitate unidirectional movement of the tubular body through the lumen of the retaining sleeve. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a side view of a patient in surgery illustrating an embodiment of the access device positioned on the abdomen and in use. 
         FIG.  2    is a cross-sectional side view illustrating an embodiment of the access device, with the wound retractor retracting the vagina of a patient, and the gel cap sealing the opening of the wound retractor. 
         FIG.  3    is a front view illustrating an embodiment of the access device deployed and in use at the mouth of the patient. 
         FIG.  4    is a top view illustrated a patient in the prone position with an embodiment of the access device deployed and in use at the anus of the patient. 
         FIG.  5 A  is a picture of the components of an access device system useful for natural orifice surgery;  FIG.  5 B  is a perspective view of the retractor of  FIG.  5 A . 
         FIG.  6 A  is a perspective view of an embodiment of a natural orifice retractor having an occlusion flange.  FIG.  6 B  is a side cut away of the natural orifice retractor of  FIG.  6 A . 
         FIG.  6 C  is a side view of an embodiment of a natural orifice retractor having a compression flange.  FIG.  6 D  is a side cut away of the natural orifice retractor of  FIG.  6 C . 
         FIG.  6 E  is a perspective view of an embodiment of a natural orifice retractor having a bolster cone. 
         FIG.  6 F  is a side view of an embodiment of a natural orifice retractor having a mechanical balloon, shown in an uncompressed state.  FIG.  6 G  is a side view of the natural orifice retractor of  FIG.  6 F , shown in a compressed, or expanded, state. 
         FIG.  6 H  is a perspective view of an embodiment of a natural orifice retractor having a balloon. 
         FIG.  6 I  is a perspective view of an embodiment of a natural orifice retractor having a saddle balloon. 
         FIG.  6 J  is a perspective view of an alternative embodiment of a retractor having an inflatable member. 
         FIG.  6 K  is a cutaway side view showing the check valve and channel disposed in the tubular body of the retractor. 
         FIG.  6 L  is a perspective view of an embodiment of a natural orifice retractor having a balloon and a bolster. 
         FIG.  6 M  is a perspective view of an embodiment of a natural orifice retractor adapted to provide retraction and access without insufflation, shown in an open configuration.  FIG.  6 N  is a cross-sectional view of the embodiment of a natural orifice retractor of  FIG.  6 M .  FIG.  6 O  is a close-up side view of the screw threads disposed around the retaining sleeve and the tubular body of the retractor.  FIG.  6 P  is a cross-sectional view of the embodiment of  FIG.  6 M , shown in a closed configuration. 
         FIG.  6 Q  is a close-up side view of the ratcheting mechanism for attaching the retaining sleeve to the tubular body of the retractor. 
         FIG.  7 A  is a perspective view of an obturator adapted to facilitate introduction of a natural orifice retractor into a body orifice such as a vagina.  FIG.  7 B  is a side view of the obturator of  FIG.  7 A . 
         FIG.  7 C  is a perspective view of an obturator having a straight shaft piece, adapted to facilitate introduction of a natural orifice retractor into a body orifice such as a vagina.  FIG.  7 D  is a perspective view of a retractor disposed on the obturator of  FIG.  7 C . 
         FIG.  7 E  is a perspective view of an obturator, modified with an indent to provide clearance for the inflation port shown in  FIGS.  61  and  6 J  and adapted to facilitate introduction of a natural orifice retractor into a body orifice such as a vagina. 
         FIG.  8 A  is a side view of the natural orifice access device of  FIG.  5 A . 
         FIG.  8 B  is a top view of the natural orifice access device illustrated in  FIG.  5 A .  FIG.  8 C  is a perspective view of the natural orifice access device illustrated in  FIG.  5 A . 
         FIG.  9 A  is a perspective view of an embodiment of a natural orifice access device including a cap having a plurality of ports extending there through. 
         FIG.  9 B  is an exploded view of an embodiment of a port and optional obturator, which is a component of some embodiments of the access device system. 
         FIG.  10 A  is a top perspective view of an embodiment of a gel cap.  FIG.  10 B  is a bottom view of an embodiment of a cap ring. 
         FIG.  11 A  is a top view of an embodiment of a gel cap comprising a plurality of access ports embedded in the gel pad.  FIG.  11 B  is a top perspective view of the gel cap illustrated in  FIG.  11 A .  FIG.  11 C  is a bottom perspective view of the gel cap illustrated in  FIG.  11 A . 
         FIG.  11 D  is a top perspective view of the gel cap illustrated in  FIG.  11 A  with instruments inserted through two of the access ports.  FIG.  11 E  is a bottom perspective view of the gel cap and instruments illustrated in  FIG.  11 D .  FIG.  11 F  is a side view of the gel cap and instruments illustrated in  FIG.  11 D . 
         FIG.  11 G  is a top perspective view of an embodiment of gel cap comprising a fixed camera or laparoscope port. 
         FIG.  12    is a cutaway perspective view of an embodiment of an access device system comprising a gel cap that snap fits to a retractor. 
         FIG.  13    is an exploded view of an embodiment of a trocar. 
         FIGS.  14 A and  14 B  are side views of an embodiment of a trocar comprising a fixation cannula in an insertion configuration and a fixation configuration, respectively. 
         FIG.  15    is a side view of another embodiment of a trocar comprising a fixation cannula. 
         FIG.  16 A  is a side view of another embodiment of a trocar comprising a fixation cannula.  FIG.  16 B  is a perspective view of an embodiment of a bolster suitable for use with the trocar illustrated in  FIG.  16 A . 
         FIG.  17 A  is a side view of another embodiment of a trocar comprising a fixation cannula.  FIG.  17 B  is a perspective view of an embodiment of a bolster suitable for use with the trocar illustrated in  FIG.  17 A . 
     
    
    
     Similar components have similar reference numbers throughout. 
     DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS 
     Embodiments of a surgical instrument access device system are useful, for example, for single incision, single port, and/or limited port laparoscopic surgical procedures, for example, abdominal ( FIG.  1   ), transvaginal ( FIG.  2   ), transoral ( FIG.  3   ), and transanal ( FIG.  4   ) procedures. Various surgical instrument access devices are described in U.S. Patent Application Publication No. 2009/0187079, entitled “SURGICAL INSTRUMENT ACCESS DEVICE,” filed Jan. 22, 2009, and U.S. Pat. No. 7,727,146, entitled “WOUND RETRACTOR WITH GEL CAP,” both of which are incorporated by reference in their entireties herein. 
       FIG.  5 A  shows an embodiment of an access device system comprising a retractor  6100 , an introducer  6400  shown inserted into the retractor as if for placement in a body orifice, a cap  6200 , one or more ports  6310 , and an obturator  6600 , which is useful in single port and/or limited port procedures. The retractor  6100  is placed and/or positioned into, across, and/or through a surgical incision and/or body orifice to enlarge, reshape, and/or isolate the incision or body orifice. The cap  6200  provides an artificial body wall through which instruments access the interior of a patient&#39;s body, for example, a body cavity, through ports  6310 . The retractor  6100  may be introduced into an orifice using the introducer  6400 ; ports  6310  may be placed through the gel cap using obturator  6600 . The components of the access device comprise any suitable biologically compatible materials. 
     With the gel cap  6200  attached to the retractor  6100 , the access device system allows the user to insufflate the orifice, such as the vaginal canal. The distention of the canal caused by the insufflation provides greater visualization of the anatomy (when compared, for example, to traditional vaginal hysterectomy) and removes the need for the use of rigid mechanical retractors which may cause damage to soft tissues. The gel cap may be detached at any point during the surgical procedure to allow for specimen removal. 
     The retractor  6100  is made of a semi-pliable thermoplastic elastomer or thermoset polymer. For use in vaginal procedures, a length of approximately 4 cm to 7 cm and a diameter of approximately 3 cm to 5 cm will suit a range of anatomies. The retractor retracts and occludes the vagina. Suture ties  6160  at proximal end  6152  and/or a flange  6110  along the tubular body may help prevent the retractor from dislodging once placed. The gel cap  6200  may be attached with the aid of a lever  6135  which locks under the proximal ring  6120  of the retractor  6100 . This creates a pressure resistant seal and insufflation is possible through insufflation ports  6145  on the gel cap. Smoke evacuation is possible through the port not being used for insufflation. Instrument ports  6310  may be placed in the gel cap  6200  to allow for the use of various laparoscopic instruments. The gel cap may then be detached and specimens may be removed through the retractor  6100 . 
     Turning to  FIG.  5 B , the outer ring  6120  is proximal a funnel section  6140 . In the illustrated embodiment, the outer ring  6120  has a substantially circular footprint. As further discussed herein, the outer ring  6120  can be sized and configured to sealingly couple to a cap or other access device thereon. In some embodiments, one or more suture points  6160  can be disposed on the retractor  6100  adjacent the outer ring  6120 . Two suture points  6160  are generally diametrically opposed relative to the generally circular profile of the outer ring  6120 . In other embodiments, the retractor can include more or fewer than two suture points disposed of various locations relative to the outer ring  6120 . 
     With continued reference to  FIG.  5 B , the tubular body  6130  has a generally circular profile defining a generally cylindrical passage  6150 . The generally cylindrical passage is desirably large enough to accommodate more than one laparoscopic instrument there through such that a single natural orifice access device can be used to provide access for multiple surgical instruments in a body cavity. Moreover, generally cylindrical passage is desirably large enough such that multiple surgical instruments positioned there through can be translated or pivoted relative to one another, allowing a surgeon to manipulate the instruments as desired during a surgical procedure. The generally cylindrical passage extends between a proximal end  6152  of the retractor  6100  adjacent the outer ring  6120  to a distal end  6154  of the retractor  6100  adjacent the flange  6110 . In  FIGS.  5 A and  5 B , the tubular body  6130  has a circular cross-section. In other embodiments, the tubular body  6130  has another shape, for example, an oval cross section, an octagonal cross-section, or other shapes as may be appropriate for the natural orifice of interest. Some embodiments of the tubular body  6130  comprise one or more coatings that provide additional functionality, for example, an anti-microbial coating. 
     In the illustrated embodiment, the funnel segment  6140  provides a diametric reduction between the relatively large diameter of the outer ring  6120 , which is sized and configured to be removably coupled to an access device such as a cap, and the relatively smaller diameter of the passage  6150 , which is sized to fit within a natural orifice with minimal distention of the orifice. The funnel segment  6140  has an inner surface which can provide a bearing surface for an obturator or introducer used to advance to the retractor  6100  into a body cavity. In some embodiments, the funnel segment can have a substantially linear taper between the relatively large diameter and the relatively smaller diameter such that the inner surface is a frustoconical segment. In other embodiments, the funnel segment  5  can have a curved profile between the relatively large diameter and the relatively smaller diameter. In some embodiments, there is no funnel section at all, as where the tubular body connects directly to the outer ring. 
     It can be desirable that the outer ring  6120  is relatively stiff compared with the relatively flexible tubular body  6130  of the retractor  6100  so that the outer ring  6120  can sealingly engage an access device such as a cap. With reference to  FIG.  5 B , a perspective view of the retractor is illustrated with a partial cutaway of the outer ring  6120 . In the illustrated embodiment, the outer ring  6120  includes an annular groove  6122  formed therein in which a reinforcing member  6124  is disposed. In some embodiments, the reinforcing member  6124  can comprise a metallic member such as a wire formed into a ring shape. For example, in some embodiments the reinforcing member  6124  can comprise a stainless steel ring positioned within the groove  6122  during manufacture of the retractor  6100 . In other embodiments, the reinforcing number  6124  can comprise an injectable nonmetallic member. For example, in some embodiments, a glass filled polymer or polycarbonate material can be injected into the groove  6122  during manufacture of the retractor  6100 . 
     While the illustrated embodiments of retractor  6100  include a reinforcing member to enhance the rigidity of the outer ring  6120 , in other embodiments, the retractor  6100  can be formed in a multiple-shot molding process. For example, in some embodiments, an inner segment of the retractor defined by the tubular body  6130  and the flange  6110  is formed in one molding operation from a flexible material, and an outer segment of the retractor  6100  defined by the funnel segment  6140  and the outer ring  6120  is formed in another molding operation from a relatively rigid material such as a polycarbonate material or other suitable material. 
     With continued reference to  FIG.  5 B , the illustrated embodiment includes a continuous generally annular groove. In other embodiments, a plurality of noncontiguous recesses can each receive one of a plurality of reinforcing members. Moreover, in some embodiments, the outer ring can include two or more concentric generally annular grooves, which each receive a corresponding reinforcing member. 
     Various types of flanges may be used to help secure the retractor in the body orifice. One embodiment of the natural orifice access device retractor  6100  illustrated in  FIG.  6 A  can be adapted for use in a transvaginal surgical procedure. The retractor  6100  comprises an occlusion flange  6111 , an outer or proximal ring  6120 , and a tubular body  6130  and a funnel segment  6140  extending between and coupling the occlusion flange  6111  and the outer ring  6120 . The occlusion flange  6111  is semi-rigid, with a diameter from approximately 2 inches to 4 inches. When inserted into the orifice, for example, the vagina, the flange is under compression from the walls of the vaginal canal, creating a seal to aid in the maintenance of insufflation. In some embodiments, the occlusion flange is “cup-shaped” with a circular ridge  6109  circumscribing a channel  6107 , which provides sufficient flexibility to allow the flange  6111  to flex to accommodate different anatomies while still maintaining a seal. 
     With reference to  FIG.  6 C , a side view of a retractor  6100  for use in the natural orifice access device system having a different flange embodiment is shown. In this embodiment, the retractor  6100  is shown with a compression flange  6112 . The compression flange  6112  is approximately 2 inches to 4 inches in diameter and is disposed around the retractor distal to the outer or proximal ring  6120 . The distance between the compression flange and the outer ring is designed to be less than the thickness of the tissues comprising the natural orifice opening. In the case of the vaginal opening, the distance is approximately 0.1 inches to 0.5 inches. This creates a compressive force on the tissue between the flange and outer ring of the retractor. This force and the “cup-shaped” geometry of the flange (see  FIG.  6 D ) occlude the vagina and serve to prevent dislodging. Suture ties  6160  may be used to mitigate dislodging. 
     With reference to  FIG.  6 E , a perspective view of a retractor  6100  for use in the natural orifice access device system having still another flange embodiment is shown. In this embodiment, the retractor  6100  is shown with a bolster cone  6113 . The soft thermoset polymer or thermoplastic elastomer bolster cone (tapered with maximum diameter approximately 2 inches to approximately 4 inches for use in the vagina) may be added to the retractor. In use, the retractor is advanced into the body orifice, such as a vagina, while the bolster cone serves as a stop to externally occlude the vagina. The bolster cone may be fixed or mobile along the tubular body  6130  of the retractor  6100 . The suture ties  6160  prevent the retractor from dislodging and maintain compression of the bolster cone against the orifice opening. The design may optionally include a flange similar to others described herein. 
     With reference to  FIGS.  6 F and  6 G , a side view of a retractor for use in the natural orifice access device system having a different flange embodiment is shown. In this embodiment, the retractor is shown with a mechanical expanding feature (a “mechanical balloon”)  6114 . The mechanical balloon comprises a series of arms  6105  that run circumferentially around the channel  6130 , the arms attached at to a first ring  6103  and a second ring  6101 . The first ring is movable along the length of the channel, while the second ring is fixed at or near the distal end of the channel. A sliding third ring  6102 , disposed around the tubular channel proximal to the first ring, may be advanced toward the distal end of the channel, putting the arms under a load that causes them to flare outwards to assume a balloon-like shape, shown in  FIG.  6 G . The arms exert a force on the anatomy of the natural orifice, causing the retractor to be anchored in place without damaging the surrounding tissue. 
     In some embodiments, the sliding third ring is threaded along its interior surface and is adapted to engage with threads disposed around the channel. See  FIG.  6 G . In other embodiments, a ratcheting mechanism may be used to move the sliding third ring along the channel. 
     The sliding ring may comprise any rigid or semi-rigid material, plastic or metal, while the arms may comprise a semi-rigid metal or plastic sufficiently flexible to flare outwards under a load. Alternatively, the arms may comprise a rigid material with an articulating joint located approximately mid-length of each arm, facilitating a similar flaring. 
     The mechanical balloon has a diameter of approximately 2 inches to approximately 4 inches and is disposed around the tubular body at the distal end of the retractor. The mechanical balloon may be coated in a non-porous, flexible material to permit occlusion and prevent dislodging when expanded or non-coated to serve solely for fixation. The amount of expansion may be variable to accommodate different anatomies. The feature is initially unexpanded to ease insertion and is then expanded as needed. 
     In some embodiments, the mechanical balloon may be used in combination with a compression flange as shown in  FIG.  6 C . In this embodiment, the compression flange is disposed around the tubular body proximal to the mechanical balloon and helps seal the retractor within the natural orifice. In an alternative embodiment, the mechanical balloon may be used in combination with a bolster cone, as shown in  FIG.  6 E . The bolster cone will act to seal the retractor within the orifice while the mechanical balloon helps anchor it. 
     In other embodiments, shown in  FIGS.  6 H-J , the flange can comprise an inflatable member  6132  such as an annular balloon coupled to a gas or fluid source that can be selectively inflated and deflated between a deflated, relatively small diameter state for insertion and removal, and an inflated, relatively high diameter state for retention in a body cavity. An inflation port  6134 , for example a check valve, affixed to the funnel portion  6140  of the retractor, is connected to the inflatable member  6132  through a channel  6136  within the wall of the tubular body  6130 . Fluid or gas introduced through the inflation port flows through the channel into the inflatable member to thereby inflate the member. 
     The channel  6136  runs through the tubular body, generally parallel to the longitudinal axis of the tubular body, with a proximal opening interacting with the inflation port  6134  and a distal opening  6139  into outer surface of the tubular body at the inflatable member. In one aspect, the inflation port  6134  may include a normally closed check valve having a spring-loaded plunger. In a further aspect, the check valve may include a Luer lock. It is contemplated that other inflation ports that are well known in the art may be used. 
     In this embodiment, the tubular body  6130  is preferably comprised of a relatively rigid material, such as a polycarbonate. The tubular body has an inflatable member at the distal end that may be created by heat shrinking polyolefin tubing around the outside of the tubular body. The distal end of the body/tubing assembly is then heated for approximately 30 to 40 seconds, and then placed inside a mold and injected with air to give the inflatable member an annular balloon shape as seen in FIG.  6 H, or any other desired shape, depending on the configuration of the mold. The inflatable member  6132  should have sufficient impermeability properties to substantially prevent inflation gas or fluid from permeating through a wall of the inflatable member. 
     In one embodiment, the inflatable member  6132  may include a substantially toroid shape upon inflation (see  FIG.  6 H ). In another embodiment, the inflatable member may include a disc shape upon inflation. In another embodiment, the inflatable member  6132  may be a fluted balloon. In still another embodiment, the inflatable member is a saddle shaped balloon  6116 , as shown in  FIG.  6 I . For use in vaginal surgery, the saddle shaped balloon in this embodiment is tapered with maximum diameter from approximately 2 inches to approximately 4 inches. The balloon is initially deflated for ease of entry into the vagina and then may be inflated by through an inflation port  6134  on the proximal end of the retractor. The vaginal opening seats in the low point of the saddle and is compressed between the peaks of the saddle as the balloon is inflated. This occludes the vagina, both internally and externally, and prevents dislodging. The balloon also distributes forces applied during the procedure over a greater area, reducing possible damage to tissue. Suture ties may also be used to mitigate dislodging. The balloon is then deflated upon completion of the procedure to ease removal. Other shapes suitable for particular natural orifices will be appreciated by one skilled in the art. 
     In use, the inflatable member may be inflated after the retractor is disposed within the natural orifice by inserting a syringe into the valve  6134  located at the proximal end  6138  of the channel within the tubular body (see  FIG.  6 K ). As shown in  FIGS.  6 J and  6 K , the port leads into the channel  6136 , which allows the fluid or gas from the syringe to travel to the inflatable member  6132 . Alternatively, a bulb pump or other source of gas or fluid may be used to inflate the inflatable member. 
     In still another embodiment, the bolster cone described herein may be combined with an inflatable member, as shown in  FIG.  6 L . In this embodiment, the retractor has a balloon  6132  at the distal end and a bolster cone  6113  mid-channel. For use in vaginal procedures, the balloon has a diameter from about 2 inches to about 4 inches while the bolster cone is tapered with a maximum diameter of about 2 inches to about 4 inches. The balloon  6132  is initially deflated for ease of entry into the vagina and then may be inflated through a port  6134  on the proximal end of the retractor. The amount of inflation may be variable to accommodate different anatomies. The balloon occludes the vagina when inflated and prevents the retractor from dislodging while causing compression of the bolster cone against the vaginal opening to further occlude. The bolster cone distributes forces applied during the procedure over a greater area, reducing possible damage to tissue. Suture ties may also be used to mitigate dislodging. The balloon is then deflated upon completion of the procedure to ease removal. 
     Another embodiment of the natural orifice access system, configured to provide retraction and access without using insufflation gases, is shown in  FIGS.  6 M- 6 P . In some natural orifices, for example, the vagina, pressure from a standard insufflator can be insufficient to maintain a visible, stable surgical working space due to leaks and billowing created by surges from the insufflator. In this embodiment, the retractor  6100  has a proximal ring  6120  and a tubular body  6130 , with the tubular body adapted to engage a retaining sleeve  6143 . The retaining sleeve includes a lip  6144  at the proximal end and at least two retracting arms  6146  at the distal end. The retracting arms are connected to the retaining sleeve with an articulating hinge  6147  that allows the arms to move between a closed position ( FIG.  6 P ), in which the distal ends of the arms in proximity, and an open position ( FIGS.  6 M,  6 N ), in which the distal ends of the arms are moved away from each other. Optionally, the retracting arms may include an angled lead  6148  near the hinge  6147 . 
     In the embodiment of  FIGS.  6 M- 6 P , the tubular body includes an external thread  6149  wrapped around the exterior of the tubular body, adapted to engage an internal thread  6151  disposed around the surface of the interior lumen of the retaining sleeve  6143 . See  FIG.  6 O . 
     In an alternative embodiment, a ratcheting mechanism comprising teeth  6153  and a series of pawls  6155  may be used instead of internal and external threads (see  FIG.  6 Q ). The ratchet mechanism allows the retractor to advance through the lumen of the retaining sleeve with relative ease while resisting backwards movement until the sides of the tubular body of the retractor are manually depressed to release the ratchet mechanism. 
     In use, the tubular body  6130  of the retractor  6100  is advanced forward through the lumen of the retaining sleeve  6143  until contact is made with the retracting arms  6146 . The angled lead  6148  on the retracting arm allows for the opening to occur at an incremental rate to accommodate a variety of anatomies. The lip  6144  on the retaining sleeve ensures that the proximal end of the lumen will not enter the orifice and provides a holding point during the advancement of the retractor. As seen in  FIGS.  6 M and  6 N , the fully advanced channel presses on the retracting arms, causing them to flare out and hold open the vaginal canal. With the tissue of the vaginal canal retracted, direct access is available to the cervix and surrounding tissue. In  FIG.  6 P , the retractor is drawn back; the retracting arms are disengaged and are able to fold together. This state facilitates insertion and removal from the orifice. 
     In some embodiments, a natural orifice access system can include a retractor  6100  and an optional obturator  6400  ( FIG.  7 A- 7 B ). The obturator can have a proximal bearing surface  6410  sized and configured to bear against the inner surface  6142  of the funnel segment  6140  and a distal dilation surface  6420  sized and configured to expand a natural orifice for passage of the retractor  6100 . Thus, during insertion of the retractor  6100  into a natural orifice, the dilation surface  6420  expands a pathway to a surgical site in a body cavity while the obturator bears on the inner surface  6142  of the funnel segment  6140  to advance the retractor  6100  into position in the surgical site. Furthermore, in some embodiments, the obturator can have a handle  6430  at a proximal end thereof adapted to facilitate selective twisting or rotation of the obturator about a longitudinal axis thereof during insertion. 
     In an alternative embodiment, shown in  FIG.  7 C , the obturator  6405  includes a straight shaft piece  6425  between the distal dilation surface  6420  and the proximal bearing surface  6410  that facilitates dilation of the natural orifice prior to inserting the retractor. It can then be combined with the retractor  6100  to help ease insertion, as shown in  FIG.  7 D . 
     In embodiments having an inflatable member on the retractor, the optional obturator  6400  may be modified with an indent  6139  to provide clearance for the inflation port, as shown in  FIG.  7 E . 
     With reference to  FIG.  8 A , a side view of a natural orifice access device having a cap  6200  removably coupled to a retractor  6100  is illustrated. In the illustrated embodiment, the cap  6200  comprises a sealable access surface  6210  such as a gel pad surface as described in further detail herein. In certain embodiments, the cap  6200  can also comprise at least one gas or fluid port  6220 ,  6230 . In the illustrated embodiment, the cap  6200  comprises two gas or fluid ports  6220 ,  6230 , such that one port can be used for gas insufflation and the other port can be used for ventilation for example when electrosurgery is performed through the access device. In certain embodiments, at least one of the gas or fluid ports  6220 ,  6230  comprises a valve such as a stopcock valve to selectively control the flow of fluid there through. 
     With reference to  FIG.  8 B , a top view of the natural orifice access device is illustrated. The sealable access surface  6210  can be encircled by and restrained by an annular frame  6240  such as a split ring having a clamp  6250 . The clamp  6250  can be movable between an open configuration in which the cap  6200  is selectively removable from the retractor  6100  and a clamped configuration in which the cap  6200  can be secured to the retractor  6100 . For example, the annular frame  6240  can be positioned peripherally around the outer ring  6120  with the clamp  6250  in the open configuration and the clamp moved to the clamped configuration to sealingly fix the cap  6200  to the retractor  6100 . Accordingly, the cap  6200  can be easily removed during a surgical procedure to facilitate removal of excised tissue from a surgical site through the retractor  6100 . 
     With reference to  FIG.  8 C , a perspective view of the natural orifice access device is illustrated. In the illustrated embodiment, the clamp  6250  can have a distal flange  6252  positioned to interface with the outer ring  6120  of the retractor when the clamp is in the clamped configuration. As illustrated, the clamp  6250  engages a distal surface of the outer ring  6120  of the retractor  6100 . In some embodiments, the annular frame  6240  can further comprise at least one distal flange sized and positioned to interface with a retractor. In the illustrated embodiment, the annular frame  6240  comprises a distal flange  6260  positioned to engage a distal surface of the outer ring  6120  of the retractor. As illustrated, the flange  6260  is generally diametrically opposed to the distal flange of the clamp  6250 . In other embodiments, the annular frame  6240  can include more than one distal flange positioned substantially equally spaced about the periphery of the annular frame  6240  or spaced irregularly about the periphery of the annular frame. 
     With reference to  FIG.  9 A , another embodiment of natural orifice access device is illustrated with a cap  6300  removably coupled to a retractor  6100 . In the illustrated embodiment, the cap  6300  includes multiple ports  6310  positioned through an access surface  6320  thereof. Advantageously, the multiple ports  6310  allow for easy placement and manipulation of multiple laparoscopic instruments in a surgical site through a single natural orifice. 
     In the illustrated embodiments of  FIG.  9 A , the ports  6310  have a relatively low profile, that is, protrude minimally above the access surface  6320  and/or below the distal surface of the cap  6300 . Accordingly, the ports  6310  are shorter than a length of a typical trocar and comprise a seal assembly positioned above the access surface  6320  and a cannula extending through the gel pad of the cap  6300 . The reduced length of the ports  6310  allows increased angular or pivotal motion for instruments extending there through, and also permits the use of curved and/or angled instruments. 
       FIG.  9 B  is an exploded view of an embodiment of a port  6310  and optional obturator  6600 , which is a component of some embodiments of the access device system. In the illustrated embodiment, the obturator  6600  comprises a pointed, puncture tip  6610 . 
     The port  6310  comprises a proximal end, a distal end, and a longitudinal axis. The port  6310  comprises a cannula  6620  extending along the longitudinal axis. A seal  6630  is disposed at the proximal end of the cannula  6620 , contained within a housing  6640 . A retainer  6650  is disposed at the distal end or tip of the cannula  6620 . 
     The cannula  6620  comprises a tubular body dimensioned to accommodate an instrument or instruments received there through. In the illustrated embodiment, the cannula  6620  is a substantially cylindrical tube, and extends through the cap  6300  in use. In the illustrated embodiment, the cannula  6620  is comparatively short because the cannula need only traverse the cap  6300  ( FIG.  9 A ), which has a known and consistent thickness, rather than a body wall. Accordingly, some embodiments of the cannula  6620  are not more than about 2-times longer, about 1.5-times longer, about 1.2-times longer, or about 1.1-times longer than the thickness of the gel pad. In some embodiments, the cannula  6620  is less than about 20 mm, about 10 mm, or about 5 mm longer than the thickness of the gel pad. In some embodiments, the cannula  6620  is about as long as the gel pad is thick. In other embodiments, the cannula  6620  has a different length, for example, a length typical for a cannula used for traversing a body wall. Shorter length cannula permit increased angular degrees of freedom for instruments passing there through. Embodiments of shorter cannula also accommodate curved instruments. The cannula  6620  comprises any suitable biocompatible material. In some embodiments, the cannula  6620  comprises a flexible material. 
     The illustrated seal  6630  comprises an instrument or septum seal  6660  and a zero seal  6670 . Optionally, a shield  6680  may be disposed within the instrument seal  6660 . The instrument seal  6660  seals instruments passing there through, thereby maintaining pressurization in a body cavity such as pneumoperitoneum or pneumorectum. The zero seal  6670  provides a seal when no instrument passes through the seal  6630 . The instrument seal  6660  and zero seal  6670  are received in a housing  6640  disposed at the proximal end of the cannula  6620  and secured therein by a seal cover  6690 . 
     The retainer  6650  is disposed at or near the distal end of the cannula  6620 . In some embodiments, the retainer  6650  and cannula  6630  are integrated, while in other embodiments, the retainer  6650  and cannula  6630  are not integrated. In the illustrated embodiment, the proximal end of the retainer  6650  comprises a flange  6655  that is generally flat and perpendicular to the longitudinal axis, while the distal end is tapered, narrowing toward the distal end of the cannula  6620 . The flange  6655  reduces the likelihood of accidental or inadvertent removal of the port  6310  from the cap. Some embodiments of the proximal face of the flange  6655  comprise additional anchoring features, for example, at least one of barbs, spikes, ridges, texturing, and the like, which are configured to penetrate or bite into a distal face of the cap  6300 . In some embodiments, a diameter of the flange  6655  is from about 1.2 to about 2.5 times wider, or from about 1.5 to about 2.0 times wider than an outer diameter of the cannula  6630 . Some embodiments of the port  6310  are 5-mm trocars, in which the outer diameter of the cannula  6620  is from about 7 mm to about 8 mm. 
     The tapered end of the retainer  6650  facilitates insertion of the port  6310  through the cap, either by itself, or when assembled with the obturator  6600  extending there through. For example, in some embodiments, the retainer  6650  is inserted through a preformed opening in the cap  6300 . 
     In some embodiments in which the retainer  6650  and cannula  6620  are not integrated, that is, are separate components, the retainer  6650  is secured to the cannula  6620  after the cannula  6620  is inserted through the cap. In some embodiments, the cannula  6620  and retainer  6650  are secured mechanically, for example, using latches, screw threads, clips, lock rings, ratchets, and the like. In some embodiments, the cannula  6620  and retainer  6650  are secured adhesively. In some embodiments, the position of the retainer  6650  is adjustable, for example, to accommodate caps of different thicknesses. In some embodiments, the cannula  6620  and/or retainer  6650  is secured to the cap, for example, adhesively. 
       FIG.  10 A  illustrates in perspective an embodiment of a cap or cover  10500 , which is a surgical access device that seals the opening between the body cavity and the area outside the body cavity while providing access into the body cavity from outside the body cavity. More particularly, the illustrated cap  10500  releasably and sealingly couples to the outer ring  6120  ( FIG.  5   ), of the wound retractor. The cap  10500  comprises a cap ring  10510  dimensioned and configured for coupling to the outer ring  6120  of the wound retractor and a pad  10530  coupled to the cap ring  10510 . Embodiments of the cap  10500  provide an artificial body wall with consistent properties compared with a natural body wall, for example, thickness, compliance, rigidity, uniformity, and the like. 
     The illustrated cap or cover  10500  is substantially circular. In other embodiment, the gel cap  10500  has another shape or footprint, for example, oval, elliptical, parabolic, square, rectangular, or another suitable curved or polygonal shape. In some embodiments, the outer ring  6120  of the retractor and cap ring  10510  of the cap have the same general shape or footprint. In other embodiments, the outer ring  6120  of the retractor and cap ring  10501  of the cap have substantially different shapes, for example, a generally circular outer ring  6120  and an oval cap ring  10510 . In these embodiments, the outer ring  6120  is distorted or reshaped for coupling to the cap ring  10510 , for example, by compressing opposed sides of the outer ring  6120 . Non-circular shapes are useful, for example, for procedures in which space is limited. As discussed above, retracting a long, straight incision using an oval or elongated retractor requires less force than a similar procedure using a circular retractor. 
     In some embodiments, the pad  10530  comprises a gel. In such embodiments, the pad  10530  is referred to as a “gel pad” and the cap  10500  is referred to as a “gel cap”. Descriptions of gel pads and gel caps generally apply to embodiments in which the pad  10530  does not comprise gel unless otherwise specified. In some embodiments, the gel pad  10530  does not comprise any preformed access channels there through, for example, for instrument access. Instruments may be inserted directly through the gel pad  10530 , puncturing the gel pad  10530 , and thereby creating access channels or portions in the gel pad  10530 . Each access portion forms an instrument seal in the presence of an instrument inserted there through and a zero seal in the absence of an instrument inserted there through. The gel provides a gas tight seal around a variety of shapes and sizes of instruments inserted there through. Some embodiments of the gel pad  10530  also provide trocar access directly there through, which also provide instrument access into the body cavity. Embodiments of the gel pad  10530  have a working diameter of from about 40 mm to about 120 mm, which is the diameter of a portion of the gel pad  10530  through which instruments and/or trocars may be inserted. Embodiments of the gel cap  10500  are typically from about 10 mm to 50 mm wider than the working diameter. 
     Accordingly, embodiments of the gel cap  10500  maintain pressurization within a body cavity such as pneumoperitoneum or pneumorectum during multiple instrument exchanges and substantially prevent unintentional loss of pressurization. Embodiments of the gel cap  10500  also provide substantially continuous access and visibility during surgery. Embodiments of the gel cap  10500  have a small profile for use in procedures with limited surgical space. 
     In some embodiments, the gel is an ultragel, which is characterized by an ultimate elongation greater than about 1000 percent and a durometer less than about 5 Shore A. Some embodiments of the ultragel comprising KRATON® and mineral oil exhibit an ultimate elongation exceeding about 1500 percent and improved sealing properties, for example, sealing with instruments of a wider size range than other seal materials. In some embodiments, the seals comprising ultragels also form zero seals when the instrument is removed therefrom. Accordingly, in some embodiments of seals comprising ultragels, a single seal is acts as both the instrument seal as well as the zero seal. 
     Some embodiments of the cap ring  10510  comprise a substantially cylindrical ring comprising a proximal portion, a distal portion, and a longitudinal axis extending from the proximal portion to distal portions. In other embodiments, the cap ring  10510  has another shape or footprint, for example, oval. As best seen in  FIG.  10 B , which is a bottom view of a cap ring  10510 , in the illustrated embodiment, the proximal portion of the cap ring  10510  comprises a plurality of apertures  10512  distributed about the periphery thereof. The apertures  10512  extend through a wall  10514  at the proximal portion of the cap ring. In other embodiments, the apertures  10512  are disposed in at least one member extending either longitudinally inward or longitudinally outward from the wall  10514  of the cap ring. The gel pad  10530  is disposed at the proximal portion of the cap ring  10510  in the illustrated embodiment, with portions of the gel pad  10530  extending through the apertures  10512 , thereby creating an interlocking structure between the cap ring  10510  and the gel pad  10530 , mechanically locking the cap ring  10510  and the gel pad  10530  together. 
     The distal portion of the cap ring  10510  is substantially cylindrical in the illustrated embodiment, and is dimensioned and configured to receive the outer ring  6120  ( FIG.  5   ) of the wound retractor. The cap ring  10510  comprises a latch mechanism  10516  that removably couples the cap ring  10510  to the outer ring  6120 . Those skilled in the art will understand that other mechanisms are also useful for coupling the cap ring  10510  to the outer ring  6120  of the wound retractor, for example, protruding lips, levers, clips, latches, tongues, grooves, screw threads, bayonet mounts, screws, friction fittings, compression fitting, snap caps, and the like. In the illustrated embodiment, when the outer ring  6120  of the wound retractor is received in the distal portion of the cap ring  10510 , the outer ring  6120  of the wound retractor contacts and embeds within a portion of the gel pad  10530  disposed at the distal portion of the cap ring  10510 , thereby displacing a portion of the gel, and forming a seal between the gel pad  10530 , and the outer ring  6120  and tubular body  6130  of the wound retractor. Thus, the distal portion of the gel pad  10530  is in juxtaposition with the incision or body orifice. In other embodiments, the cap ring  10510  is permanently coupled or fixed to the outer ring  6120 . 
     The cap ring  10510  in some embodiments comprises a polymer. Examples of suitable polymers include, at least one of polyethylene (PE), low density polyethylene (LDPE), high density polyethylene (HDPE), ultra high molecular weight polyethylene (UHMWPE), polycarbonate, thermoplastic elastomers (DYNAFLEX®, GLS Corp.; KRATON®, Kraton Polymers), polyphenylene oxide (PPO), polystyrene, and the like. The polymer component of the cap ring is fabricated by any suitable method, including injection molding, melt casting, blow molding, and the like. 
     Some embodiments of a process in which the gel pad  10530  is cast in the cap ring  10510  are include steps performed at temperatures above about 130° C. over several hours, for example, from about three (3) to about four (4) hours. Accordingly, in some of these embodiments, the cap ring  10510  does not deform under these conditions. 
     Some embodiments of the gel pad  10530  comprise an elastomeric gel. Examples of such gels are described in U.S. patent application Ser. No. 10/381,220, filed Mar. 20, 2003, the disclosure of which is hereby incorporated by reference as if set forth in full herein. Embodiments of the gel are prepared by mixing at least one triblock copolymer with a solvent that dissolves the midblocks of the triblock copolymer. The mixture is typically a slurry. The endblocks typically comprise a thermoplastic material, such as styrene, while the midblocks typically comprise a thermoset elastomer such as, ethylene/butylene, isoprene, or butadiene. Examples of the triblock copolymer include styrene-ethylene/butylene-styrene (SEBS), styrene-isoprene-styrene (SIS), and styrene-butadiene-styrene (SBS). In some embodiments, the solvent is an oil, for example, mineral oil. Upon heating a mixture or slurry of the triblock copolymer, the midblocks dissolve in the mineral oil, thereby forming a network of the insoluble endblocks. The resulting network has enhanced elastomeric properties compared with the parent copolymer. In some embodiments, the triblock copolymer used is KRATON® G1651, which has a styrene to rubber ratio of 33/67. Once formed, the gel is substantially permanent and, by the nature of the endblocks, processable as a thermoplastic elastomer henceforward. The mixture or slurry has a minimum temperature at which it becomes a gel, which is referred to as the minimum gelling temperature (MGT). This temperature typically corresponds to the glass transition temperature of the thermoplastic endblock plus a few degrees. For example, the MGT for a mixture of KRATON® G1651 and mineral oil is about 120° C. When the slurry reaches the MGT and the transformation to a gel state takes place, the gel becomes more transparent, thereby providing a visual endpoint confirming the complete transformation of the slurry to the gel state, whereupon the gel may be cooled. Some embodiments of the gel comprise a diblock copolymer, either instead of or in addition to the triblock copolymer. Embodiments of the diblock copolymer comprise a thermoplastic first endblock, for example, styrene, and a thermoset elastomeric second endblock, for example, ethylene/butylene, isoprene, or butadiene. An example of a suitable diblock copolymer is styrene-ethylene/butylene (SEB). 
     For a given mass of slurry to form a complete gel, the entire mass of the slurry is heated to or above the MGT and held at or above the MGT for a sufficient time for the end blocks to form a network or matrix of interconnections. The slurry will continue to form a gel at temperatures between the MGT and temperatures at which the components of the slurry/gel begin to decompose and/or oxidize. For example, when the slurry/gel is heated at temperatures above 250° C., the mineral oil in the slurry/gel will begin to be volatile and oxidize. Oxidizing may cause the gel to turn brown and become oily. 
     The speed at which a given volume of slurry forms a gel depends on the speed with which the entire mass of slurry reaches the MGT. Also, at temperatures higher than the MGT, the end block networks distribute and form more rapidly, thereby speeding the gel formation. 
     The various base gel formulas may also be mixed or alloyed with one another to provide gels with a variety of intermediate properties. For example, KRATON® G1701X is a mixture of seventy percent (70%) SEB and thirty percent (30%) SEBS, with an overall styrene to rubber ratio of 28/72. Those skilled in the art will appreciate that an almost unlimited number of combinations, alloys, and styrene to rubber ratios can be formulated, each providing and embodiment exhibiting one or more advantages, for example, low durometer, high elongation, and good tear strength. 
     Some embodiments of the gel material further comprise a polymer that, with a foaming agent, improves the sealing properties of the gel, for example, silicone, soft urethanes, and even harder plastics. Examples of suitable silicones include those used for electronic encapsulation. Examples of suitable harder plastics include polyvinylchloride (PVC), isoprene, KRATON® neat, and other KRATON®/oil mixtures. In the KRATON®/oil mixture, suitable oils include vegetable oils, petroleum oils, and silicone oils, as well as mineral oil. 
     Some embodiments of the gel comprise one or more additives that provide one or more desirable properties, for example, at least one of enhanced lubricity, improved appearance, and wound protection. Additives are incorporated directly into the gel and/or applied as a surface treatment. In some embodiments, other compounds are added to the gel to modify its physical properties and/or to assist in subsequent modification of the surface by providing bonding sites and/or surface charges. Additionally, oil-based colorants are added to the slurry to create gels of different colors in some embodiments. 
     Some embodiments of the gel pad  10530  comprise a layer of polyethylene on at least one surface. Polyethylene is dissolved in mineral oil and the solution applied to one or more surfaces of the gel pad  10530 . The mineral oil does not evaporate, but instead, absorbs into the gel pad over time, leaving behind the polyethylene as a layer on the surface of the gel pad. 
     In some embodiments, the triblock copolymer/solvent mixture/slurry used to manufacture the gel pad  10530  comprises about ninety percent (90%) by weight of mineral oil and about ten percent (10%) by weight of KRATON® G1651. From a thermodynamic standpoint, this mixture behaves similarly to mineral oil. Because mineral oil has a relatively high heat capacity, transforming 0.45 kg (1 pound) of the slurry into a homogenous gel at about 130° C. may take from bout three (3) to about four (4) hours. Once formed, the gel can be cooled as quickly as practicable with no apparent deleterious effects on the gel. In some embodiments, the gel is cooled by cold-water immersion. In other embodiments, the gel is air-cooled. Those skilled in the art will recognize that other cooling techniques are used in other embodiments. 
     Certain properties of the KRATON®/oil gel will vary with the weight ratio of the components. In general, a higher proportion of mineral oil results in a softer gel, while a higher proportion of KRATON® results in a firmer gel. A too-soft gel exhibits excessive tenting or doming of the gel cap  10500  during surgery when a patient&#39;s body cavity is insufflated. Some embodiments of gels that are too soft also do provide an adequate instrument seal and/or zero seal. The gel should be sufficiently soft to provide an adequate seal both in the presence of an instrument and in the absence of an instrument, however. 
     On prolonged or extended sitting or standing, the copolymer, such as KRATON®, and the solvent, such as mineral oil, in the slurry may separate. The slurry may be mixed to greater homogeneity, for example, with a high shear mixer. Mixing the slurry may introduce or add air to the slurry, however. To remove air from the slurry, the slurry may be degassed. In some embodiments, the slurry is degassed under a vacuum, for example, within a vacuum chamber. In some embodiments, the applied vacuum is about 0.79 meters (about 29.9 inches) of mercury, or about one (1) atmosphere. Optionally, stirring or mixing the slurry under vacuum facilitates removal of the air. During degassing under vacuum, the slurry typically expands, then bubbles, and then reduces in volume. The vacuum is typically discontinued when the bubbling substantially ceases. Degassing the slurry in a vacuum chamber reduces the volume of the slurry by about ten percent (10%). Degassing the slurry also reduces oxidation of the finished gel in some embodiments. 
     Degassing the slurry tends to result in a firmer gel. A gel made from a degassed slurry comprising about 91.6% by weight of mineral oil and about 8.4% by weight of KRATON® G1651, an eleven-to-one ratio, has about the same firmness as a gel made from a slurry that is not degassed and that comprises about ninety percent (90%) by weight of mineral oil and about ten percent (10%) by weight of KRATON® G1651, a nine-to-one ratio. 
     Because mineral oil typically has a lower density than KRATON®, the two components will separate after mixing, with the less dense mineral oil rising to the top of the container. This phase separation typically occurs when transforming a static slurry into a gel over several hours. Consequently, the resulting gel is non-homogeneous, with a higher concentration of mineral oil at the top and a lower concentration at the bottom. The speed of separation is a function of the depth or head height of the slurry being heated. Factors relevant to the relative homogeneity of the gel include the mass of slurry, the head height, the temperature at which the gel sets, and the speed at which the energy is transferred to the gel. 
     The gel pad  10530  or gel cap  10500  are gamma sterilized in some embodiments, which is relatively and/or comparatively simpler to qualify compared with other sterilization process, for example, versus ethylene oxide. Gamma sterilization can cause large bubbles to form in the gel pad, however, which are cosmetic and/or aesthetic issues in the sterilized devices. Because bubbles typically comprise greater than ninety-nine percent (99%) room air, the dissolved air is advantageously removed from the slurry prior to transforming the slurry into a gel. For example, the slurry may be degassed under vacuum, as described above, then gelled by heating. Some bubbles may still form in the gel during gamma sterilization, but typically disappear over a period of from about twenty-four (24) hours to about seventy-two (72) hours. Typically, mineral oil at room temperature has about ten percent (10%) dissolved gas. As discussed above, removing air from the gel makes the gel firmer. This effect is counterbalanced by a softening of the gel by the gamma radiation during gamma sterilization, however. 
     In some embodiments in which the gel pad  10530  is gamma sterilized, the gel comprises about ninety percent (90%) mineral oil by weight and about ten percent (10%) KRATON® by weight. As stated above, degassing the slurry makes the gel firmer. The counteracting softening by the gamma radiation, however, results in a gel with substantially the same firmness as a gel comprising about ninety percent (90%) mineral oil by weight and about ten percent (10%) KRATON® by weight that is not degassed and gamma sterilized. 
     In some embodiments, the gel pad  10530  is coupled to, attached to, formed with, or integrated with the cap ring  10510  to provide a gas-tight seal between the cap ring  10510  and the tubular body  6130  ( FIG.  5   ). The gel pad  10530  covers and seals the entire opening in the cap ring  10510 , as well as covering substantially the entire wound or orifice opening. As stated above, the gel pad  10530  provides a gas tight seal around a variety of shapes and sizes of instruments inserted there through. 
     Embodiments in which a gel pad support structure of the cap ring  10510  comprises a thermoplastic elastomer, for example, DYNAFLEX® or KRATON®, and the gel pad  10530  comprises a similar thermoplastic elastomer, for example, KRATON®, exhibit improved adhesion between the gel pad  10530  and the cap ring  10510 . The polystyrene component of KRATON® in the gel pad  10530  improves adhesion with polyphenylene oxide (PPO), polystyrene, and other similar polymers. 
     In some embodiments of cap rings  10510  comprising polycarbonate, the polycarbonate component of the cap ring  10510  does not bond with the gel pad  10530  at 130° C., which is a typical manufacturing temperature for a gel pad  10530  comprising KRATON®. Raising the temperature to about 150° C. for a few minutes during casting, however, bonds the gel pad  10530  to the cap ring  10510 . It is believed that heating the gel pad  10530  and cap ring  10510  to a temperature at which both the polystyrene component of the gel and the polycarbonate are simultaneously above their melt points allows bonds to form there between. In other embodiments, the uncured gel and the cap ring  10510  are heated to near or at the glass transition temperature of the polycarbonate in the cap ring  10510 , thereby bonding the gel pad  10530  to the cap ring  10510 . 
     In some embodiments, the gel comprises mineral oil and the cap ring  10510  comprises a polymer that dissolves in mineral oil under the manufacturing conditions, for example, polyethylene (PE), low density polyethylene (LDPE), high density polyethylene (HDPE), and ultra high molecular weight polyethylene (UHMWPE). Using polyethylene (PE) as an example, PE has a higher molecular weight than mineral oil and dissolves in mineral oil at the temperatures used to cast the gel pad  10530 . As such, as a portion of the PE in the cap ring  10510  dissolves in the mineral oil in the gel pad  10530  at the processing temperatures, for example, above about 130° C., a bond between the PE in the cap ring  10510  and gel pad  10530  is formed. 
     In an embodiment of a method for manufacturing a gel cap, the cap ring  10510  is placed into a mold that together with the cap ring  10510  includes a negative space in the desired shape of the gel pad and uncured gel is added to the mold. Sufficient uncured gel is then added to the mold to cover and fill the apertures  10512 . The uncured gel flows through, fills, and remains within the apertures. Also, in some embodiments, the mold is filled with sufficient uncured gel to extend into the distal portion of the cap ring  10510 . After the gel cures, the gel in the apertures connects and couples the gel on a first side of each aperture  10512  to the gel on a second side of the aperture, thereby mechanically locking the gel pad  10530  to the cap ring  10510 . 
     Some embodiments include another method for coupling the gel pad  10530  to the cap ring  10510 , either in addition to or instead of the mechanical interlocking discussed above. Such methods are useful, for example, for coupling separately formed gel pads or gel slugs  10530  and cap rings  10510 . Some embodiments use a glue or adhesive to couple the gel pad  10530  to the cap ring  10510 , for example, cyanoacrylate (SUPERGLUE® or KRAZY GLUE®). The glue is believed to bond to either the rubber or the styrene component of the triblock copolymer with a bond is frequently stronger than the gel material itself. Some embodiments use solvent welding in which a solvent dissolves a plastic in the cap ring  10510  and the polystyrene in the gel pad  10530 . The solvent is applied to the gel pad  10530  and cap ring  10510  by any suitable method, for example, by spraying and/or by dipping. In effect, the solvent melts both the plastic of the cap ring  10510  as well as the polystyrene in the gel pad  10530 , thereby forming a bond between the two, which remains after the solvent evaporates. 
     In an embodiment for manufacturing a gel cap  10500 , the gel pad  10530  is cast into the cap ring  10510  to form the gel cap  10500 . The cap ring  10510  is positioned in or placed into a mold cavity of a casting mold. Embodiments of the mold cavity include support for the annular walls of the cap ring  10510 . Embodiments of the mold comprise a material with sufficient heat dissipation properties, for example, at least one of aluminum, copper, and brass. Those skilled in the art will recognize that other mold materials with lower heat dissipation properties will produce acceptable parts in some embodiments. Furthermore, some embodiments of the mold comprise active cooling elements, for examples, channels through which coolants are pumped. 
     The mold cavity and cap ring  10510  assembly is then filled with a desired amount of the triblock copolymer/mineral oil slurry such that the slurry contacts the cap ring  10510 . In some embodiments, the slurry is preheated, for example, to about 52° C. (125° F.), which facilitates a complete filling of the mold cavity by the slurry, thereby reducing the probability of voids in the gel. Preheating the slurry to a temperature below the MGT reduces the viscosity of the slurry and allows the slurry to flow more easily. As stated above, some embodiments of the slurry are degassed in a vacuum before casting. In some embodiments, the slurry is also degassed after it is filled in the mold cavity to remove any air that may have been introduced during the filling of the mold cavity, as well as to facilitate flow of the slurry into voids in the mold. The mold, cap ring, and slurry are heated, for example, in an oven, until the slurry reaches a temperature of about 150° C. As stated above, the slurry turns into gel at about 120° C.; however, at about 150° C., the gel bonds to a polycarbonate cap ring  10510 . Depending on the material used in the cap ring  10510 , bonding may take place at a temperature other than about 150° C. In embodiments in which the cap ring  10510  is comprises a material with a lower melting point than the MGT, for example 120° C., the gel pad  10530  is molded separately as a gel slug, which is then bonded to the cap ring  10510  as discussed above. 
     When the transformation of the slurry into a gel is complete, for example, when the temperature of the gel pad reaches about 150° C., the gel cap  10500  is cooled, for example, by air-cooling, cold-water immersion, or another suitable method. At 150° C. the gel pad  10530  is soft and easily distorted. Distortions in the gel pad  10530  present during cooling would be set after cooling. Accordingly, in some embodiments, the gel cap  10500  is cooled within the mold, thereby reducing the likelihood of distorting the gel pad  10530 . Factors affecting the cooling time include the size and configuration of the mold, the quantity of gel, temperature and quantity of cooling medium, the properties of the cooling medium, and the mold material. As an example, the cooling time for a particular gel cap  10500  may be about two (2) hours for air cooling and about fifteen (15) minutes for water cooling. Whether cooling with air or water, the final properties of the gel are substantially the same. The gel cap  10500  is typically cooled to about ambient room temperature, but may be cooled to a lower temperature if desired. At about 0° C., the gel hardens, which is useful, for example, in secondary operations such as when coupling separately manufactured gel pads  10530  and cap rings  10510 . The gel cap  10500  may be removed from the mold at any time after the gel has set. 
     When removed from the mold, the gel pad  10530  typically has a tacky surface. Coating the gel pad  10530  with a powder, such as cornstarch, substantially reduces or eliminates the tackiness of the cured gel pad  10530 . 
     As stated above, in some embodiments, the gel pad  10530  is molded separately from the cap ring  10510 , and coupled to the cap ring  10510  in a secondary operation, for example, bonding. In some embodiments, the gel pad  10530  is molded as a gel slug with an outer perimeter smaller than the perimeter of the inner cylindrical wall of the cap ring  10510  and a height greater than the height of the cap ring  10510 . Because the gel pad  10530  is molded separate from the cap ring  10510 , the slurry need only be heated to the MGT, for example, about 120° C., to complete the transformation of the slurry into a gel, whereupon the gel becomes substantially transparent. As discussed above, the gel slug may be cooled, for example, to about 0° C., then placed within the inner cylindrical wall of the cap ring  10510 . 
     In some embodiments, the gel slug is coupled to the cap ring  10510  through compression molding, in which the gel slug is compressed longitudinally, thereby expanding the outer perimeter of the gel slug and compressing the gel slug against the inner cylindrical wall of the cap ring  10510 . The compressed gel slug and cap ring  10510  are then heated to a sufficient temperature for the polystyrene in the gel and the polymer of the cap ring  10510  to form bonds there between. Molding the gel slug separately from the cap ring  10510  followed by heat bonding the gel slug to the cap ring is especially useful in embodiments in which the cap ring  10510  comprises a material with a melting temperature lower than the MGT of the gel. In such situations, the gel slug can be molded separately and heat bonded to the cap ring  10510  without melting the cap ring  10510 . 
     An embodiment of a method for retracting an incision or body orifice using the retractor  6100 ,  7100  is discussed in detail above. The method results in the outer ring  6120  of the retractor substantially in contact with the exterior surface of the body wall. The gel cap  10510  is then coupled to the outer ring  6120  of the retractor, thereby sealing the opening between the body cavity and the area outside the body cavity and allowing the surgeon to insufflate the body cavity. 
     As discussed above, embodiments of the gel cap  10500  comprise no preformed access channels in the gel pad  10530 . In use, instruments may be inserted directly through the gel pad  10530 , thereby creating access channels through the gel pad  10530 . Each access channel created in the gel cap forms an instrument seal in the presence of an instrument passing there through because the gel provides a gas tight seal around a variety of shapes and sizes of instruments. When the instrument is removed from the gel pad  10530 , the channel created in the gel pad by the instrument closes to form a zero seal. 
     Some embodiments of the cap use access devices such as trocars inserted through the gel pad  10530  for instrument access, in particular, where an access channel experiences repeated instrument manipulation, for example, insertion, removal, advancement, retraction, rotation and/or other manipulation. Each trocar inserted through the gel pad  10530  permits repeated introduction, removal, and/or manipulation of instruments there through. 
     In some embodiments, the gel cap  10500  initially comprises no access channels, and the surgeon is at liberty to determine the placement of instruments there through. Moreover, the surgeon has unlimited flexibility in the placement and repositioning of ports within the area of the gel cap  10500 , as well as the option of selecting different trocar sizes for different clinical procedures. Being detachable, the gel cap  10500  allows for the removal of large specimens. Once removed, the gel cap  10500  can be re-coupled to the outer ring  6120  of the retractor, thereby restoring the seal and allow the surgeon to re-insufflate the body cavity. 
     Moreover, embodiments of the gel are deformable without losing physical integrity, and while maintaining substantially gas tight instrument seals with any instruments extending there through, as well as gas tight zero seals for any access channels without any instruments extending there through. Accordingly, embodiments of the gel cap  10500  permit both translational or positional, and angular or pivotal “float” or degrees of freedom for the instruments passing through the gel pad  10530 . This float permits instrument motion both relative to the cap ring  10510  as well as relative to other instruments. In contrast, other single or limited port systems do not exhibit one or both translational or angular float for instruments. 
       FIG.  11 A  is a top view of an embodiment of a gel cap  11500  comprising a plurality of access ports, seals, or sealing valves disposed in the gel pad.  FIG.  11 B  is a perspective top view of the gel cap  11500  mounted on a retractor.  FIG.  11 C  is a perspective bottom view of the gel cap  11500  mounted on a retractor. The gel cap  11500  comprises a cap ring  11510  and a gel pad  11530 , which are generally similar to the cap ring and gel pad of the embodiment described above. 
     The gel cap  11500  further comprises a plurality of access ports  11540 , at least a portion of which is disposed within or embedded within the gel pad  11530 . In the illustrated embodiment, the access ports  11540  have a low profile, that is, do not protrude or protrude minimally above the proximal surface of the gel pad  11530  and/or below the distal surface of the gel pad  11530 . Accordingly, the lengths of the access ports  11540  are similar to the thickness of the gel pad  11530 , which is shorter than a length of a typical trocar inserted in the gel pad  11530 , which comprises a seal assembly positioned above the gel pad  10530 , and a cannula extending through the gel pad  11530 . The reduced length of the access port  11540  allows increased angular or pivotal motion for instruments extending there through, and also permits the use of curved and/or angled instruments. In the illustrated embodiment, the access ports  11540  are substantially permanent or non-removable under the conditions under which the gel cap  11500  is used. Trocars can also be inserted through the gel pad  11530  if additional ports are desired. 
     Each port  11540  comprises longitudinal axis extending from a proximal side to a distal side of the gel pad  11530 , a first seal  11542  disposed at the proximal side of the gel pad  11530 , and a second seal  11544  disposed distal to the first seal  11542 . A sight of each of the ports or seals  11540  has an aperture through the gel pad  11530  and coincides with the longitudinal axis. In the illustrated embodiment, the first seal  11542  forms an instrument seal with an instrument extending there through and the second seal  11544  forms a zero seal in the absence of an instrument extending there through. 
     In the illustrated embodiment, the first seal  11542  comprises a septum seal. Each septum seal comprises an aperture  11546  there through that is slightly smaller than a cross-section of the smallest instrument to be inserted there through. The aperture  11546  of the septum seal is substantially aligned with the aperture through the gel pad and the longitudinal axis of the port  11540 . When an instrument is inserted through the aperture  11546  of the septum seal, the aperture  11546  expands and engages the outer surface of the instrument, thereby forming a seal therewith. The septum seal comprises an elastomeric material that biases the aperture against an instrument is inserted there through. Those skilled in the art will understand that other types of instrument seals are used in other embodiments. 
     In the illustrated embodiment, the second seal  11544  comprises a double-duckbill valve, which functions as a zero-closure seal that provides a zero seal in the absence of an instrument inserted there through. Those skilled in the art will understand that the second seal comprises another type of seal, for example, a duckbill valve, a flap valve, and the like. The double-duckbill valve comprises as elastomeric material. In some embodiments, each of the first seal  11542  and the second seal  11544  independently comprise an elastomeric material, for example, at least one of rubber, synthetic rubber, silicone, ethylene propylene diene monomer (EPDM), ethylene-propylene copolymer (EP rubber), polyisoprene, polybutadiene, polyurethane, styrene-butadiene, ethylene vinyl acetate (EVA), polychloroprene)(NEOPRENE®) , perfluorelastomer)(KALREZ®, and the like 
     Thus, during use, the septum seal provides an instrument seal in the presence of an instrument inserted there through, and the duckbill valve provides a zero seal in the absence of an instrument inserted there through. The illustrated embodiment comprises ports or seals  11540  in the gel pad of different sizes. Each size of port  11540  sealing accommodates a different range of instrument sizes inserted there through. The size of a port is typically given as the diameter of the largest instrument that the port will accommodate, for example, 5 mm, 11 mm, or 12 mm.  FIGS.  11 D,  11 E , and  11 F are a perspective top view, a perspective bottom view, and a side view of a thinner instrument  11550   a  and a thicker instrument  11550   b  inserted through a smaller port  11540   a  and a larger port  11540   b , respectively, of the embodiment of the gel cap  11500  illustrated in  FIGS.  11 A- 11 C . 
       FIG.  11 G  is a top perspective view of an embodiment of a gel cap  11500  further comprising a fixed port position, for example, for a camera or a laparoscope. The fixed port  11560  comprises a lock mechanism  11562  that maintaining the position of a camera or laparoscope inserted there through. In some embodiments, one of the ports  11540  further comprises a stopcock and/or gas fitting used as a gas inlet and/or outlet port for insufflating, depressurizing, and/or venting the body cavity of gas. In some embodiments, a gas inlet/outlet port is disposed on the cap ring  11510 . 
       FIG.  12    is a cutaway perspective view of an embodiment of an access device system  12000  comprising retractor  12100  and a cap or cover  12500 , which are similar to embodiments of retractors and gel caps described above. The retractor  12100  comprises an inner ring  12110 , an outer ring  12120 , and a sleeve  12130  extending between the inner ring  12110  and the outer ring  12120 . In the illustrated embodiment, the cap  12500  is a gel cap comprising a proximal side, a distal side, a cap ring  12510 , and a gel pad  12530 . In the illustrated embodiment, the cap ring  12510  comprises a tubular ring dimensioned to receive the outer ring  12120  of the retractor therewithin. The distal side of the cap ring  12510  comprises an annular slot  12520 , which is sufficiently radially deformable for the outer ring  12120  to reversibly pass there through. Accordingly, the illustrated embodiment of the cap ring  12510  secures the cap  12500  to the outer ring  12120  with a snap or friction fit. 
       FIG.  13    is an exploded view of an embodiment of a trocar  13800  and optional obturator  13900 , which is a component of some embodiments of the access device system. In the illustrated embodiment, the obturator  13900  comprises a pointed, puncture tip  13910 . In embodiments in which the trocar  13800  and obturator  13900  are inserted through a gel pad  10530  rather than a body wall, potential damage to underlying tissue by contact with the tip  13910  is reduced because the gel pad  10530  serves as an artificial body wall that is spaced from the underlying tissue as discussed above. In other embodiments, the obturator tip  13910  has another shape, for example, blunt and/or bladeless, which, for example, reduces the likelihood of damage to other components of the access system, for example, a retraction sheath of a retractor. 
     The trocar  13800  comprises a proximal end, a distal end, and a longitudinal axis. The trocar  13800  comprises a cannula  13810  extending along the longitudinal axis. A trocar seal  13820  is disposed at the proximal end of the cannula  13810 . A retainer  13830  is disposed at the distal end or tip of the cannula  13810 . In the illustrated embodiment, the distal end or tip of the cannula  13810  is not angled. Other embodiments comprise an angled distal end or tip of the cannula  13810 . The illustrated embodiment of the trocar  13800  does not comprise an insufflation gas inlet. Consequently, the trocar  13800  is typically used in procedures in which a body cavity is not insufflated, or in which insufflation is provided through another device. Other embodiments of trocars are disclosed in U.S. patent application Ser. No. 11/677,994, filed Feb. 22, 2007, the disclosure of which is incorporated by reference. 
     The cannula  13810  comprises an elongate, tubular cannula body  13812  dimensioned to accommodate an instrument or instruments received there through. In the illustrated embodiment, the cannula body  13812  is a substantially cylindrical tube, and extends through the gel pad  10530  in use. In the illustrated embodiment, the cannula body  13812  extends from the proximal end of the cannula  13810  to which the trocar seal  13820  is coupled, and which has a larger outer diameter than the cannula body  13812 . 
     In some embodiments, the cannula  13810  is comparatively short because the cannula body  13812  need only traverse the gel pad  10530  ( FIG.  10 A ), which has a known and consistent thickness, rather than a body wall. Accordingly, some embodiments of the cannula body  13812  are not more than about 2-times longer, about 1.5-times longer, about 1.2-times longer, or about 1.1-times longer than the thickness of the gel pad. In some embodiments, the cannula body  13812  is less than about 20 mm, about 10 mm, or about 5 mm longer than the thickness of the gel pad. In some embodiments, the cannula body  13812  is about as long as the gel pad is thick. In other embodiments, the cannula body  13812  has a different length, for example, a length typical for a cannula used for traversing a body wall. Shorter length cannula bodies permit increased angular degrees of freedom for instruments passing there through. Embodiments of shorter cannula bodies also accommodate curved instruments. The cannula  13810  comprises any suitable biocompatible material. In some embodiments, the cannula  13810  comprises a flexible material. 
     The illustrated trocar seal  13820  comprises an instrument or septum seal  13822  and a zero seal  13824 . The instrument seal  13822  seals instruments passing there through, thereby maintaining pressurization in a body cavity such as pneumoperitoneum or pneumorectum. The zero seal  13824  provides a seal when no instrument passes through the trocar seal  13820 . The instrument seal  13822  and zero seal  13824  are received in a housing  13826  disposed at the proximal end of the cannula  13810  and secured therein by a seal cover  13828 . 
     The retainer  13830  is disposed at or near the distal end of the cannula  13810 . In the illustrated embodiment, the distal end of the cannula  13810  is generally perpendicular to the longitudinal axis thereof, or not angled. Other embodiments comprise an angled distal end or tip. In some embodiments, the retainer  13830  and cannula  13810  are integrated, while in other embodiments, the retainer  13830  and cannula  13810  are not integrated. In the illustrated embodiment, the proximal end of the retainer  13830  comprises a flange  13832  that is generally flat and perpendicular to the longitudinal axis, while the distal end is tapered, narrowing toward the distal end of the cannula  13810 . The flange  13832  reduces the likelihood of accidental or inadvertent removal of the trocar  13800  from the gel pad. Some embodiments of the proximal face of the flange  13832  comprise additional anchoring features, for example, at least one of barbs, spikes, ridges, texturing, and the like, which are configured to penetrate or bite into a distal face of the gel pad  10530 . In some embodiments, a diameter of the flange  13832  is from about 1.5 to about 2.5 times wider, or from about 2 to about 2.2 times wider than an outer diameter of the cannula body  13812 . Some embodiments of the trocar  13800  are 5-mm trocars, in which the outer diameter of the cannula body  13812  is from about 7 mm to about 8 mm. 
     The tapered end of the retainer  13830  facilitates insertion of the trocar  13800  through the gel pad, either by itself, or when assembled with the obturator  13900  extending there through. For example, in some embodiments, the retainer  13830  is inserted through a preformed opening in the gel pad  10530 . Because embodiments of the gel material of the gel pad  10530  have high elongation values, as discussed above, the retainer  13830  is insertable through a relatively small opening in the gel pad  10530 , yet resists inadvertent removal, as discussed above. 
     In some embodiments in which the retainer  13830  and cannula  13810  are not integrated, that is, are separate components, the retainer  13830  is secured to the cannula  13810  after the cannula  13810  is inserted through the gel pad. In some embodiments, the cannula  13810  and retainer  13830  are secured mechanically, for example, using latches, screw threads, clips, lock rings, ratchets, and the like. In some embodiments, the cannula  13810  and retainer  13830  are secured adhesively. In some embodiments, the position of the retainer  13830  is adjustable, for example, to accommodate gel pads of different thicknesses. In some embodiments, the cannula  13810  and/or retainer  13830  is secured to the gel pad, for example, adhesively. 
       FIG.  14 A  is a side view of another embodiment of a trocar  14800  that is suitable as a component of a single-port surgical access system described above, for example, comprising a gel pad  10530  and retractor. Some embodiments of the access system comprise a plurality of trocars  14800 . The trocar  14800  is generally similar to the trocar  13800  described above, and comprises a cannula  14810 , a trocar seal assembly  14820 , and a retainer  14830 , which are generally similar to the corresponding features described above. The illustrated embodiment of the trocar  14800  further comprises a bolster  14840  and a locking component  14850 . The illustrated embodiment of the cannula  14810  is also referred to as a “fixation cannula” as will become apparent from the discussion below. 
     In the illustrated embodiment, the bolster  14840  comprises a torus or doughnut. A cannula body  14812  extends through an opening in the bolster  14840 . A diameter of the opening of the bolster  14840  is sufficiently larger than an outer diameter of the cannula body  14812  to permit free movement along the cannula body  14812 . The illustrated embodiment of the bolster  14840  comprises a deformable material, for example, a polymer resin and/or elastomer, as will be described in greater detail below. Examples of suitable materials include rubber, natural rubber, synthetic rubber, polyisoprene, styrene-butadiene rubber, silicone rubber, ethylene-propylene copolymer, ethylene-propylene-diene monomer rubber, polybutadiene, polychloroprene, polyurethane, and the like. Some embodiments of the bolster  14840  comprise a lubricious layer or coating in an area or region that contacts the cannula  14810 , which facilitates movement along the cannula  14810 . 
     An outer diameter of some embodiments of the bolster  14840  is from about 0.8 to about 2 times, or from about 1 to about 1.5 times a diameter of a flange  14832  of the retainer  14830 . A thickness of the bolster is from about 3 mm (0.12 inch) to about 10 mm (0.4 inch), or from about 4 mm (0.16 inch) to about 6 mm (0.24 inch). In some embodiments, a distal face  14844  of the bolster is concave, thereby providing additional clamping or fixation force on the gel pad  10530 , as well as conforming to gel pads  10530  with different and/or non-uniform thicknesses. The particular dimensions of the bolster  14830  are selected based on the properties of the bolster material and the gel material, and the dimensions of the cannula body  14812 , the locking component  14850 , and the gel pad  10530 . 
     The locking component  14850  is disposed on the cannula body  14812  proximal of the retainer  14830 , and comprises a lip  14852  proximal of an enlarged section  14854 . The lip  14852  extends radially from the cannula body  14812  with a diameter greater than the diameter of the opening of the bolster  14840 . The elastomeric material of the bolster  14840  permits the bolster  14840  to be urged over and past the lip  14852 . In the illustrated embodiment, the lip  14852  comprises a ratchet dimensioned to facilitate the bolster  14840  sliding distally and to resist the bolster  14840  from sliding proximally. Also, in the illustrated embodiment, the lip  14852  is a continuous structure encircling the cannula body  14812 . In other embodiments, the lip  14852  comprises a plurality of structures disposed around the cannula body  14812 . 
     The enlarged section  14854  is generally cylindrical with a diameter that is about the same as or slightly larger than the diameter of the opening in the bolster  14840 , thereby frictionally engaging the bolster  14840  thereto. In the illustrated embodiment, the enlarged section  14854  is longer than a thickness of the bolster  14840 . In the illustrated embodiment, the enlarged section  14854  does not extend to or contact the flange  14832  of the retainer  14830 , thereby not reducing a surface area of a proximal face thereof, and thereby improving the removal resistance thereof. In other embodiments, the enlarged section  14854  extends to the retainer  14830 . Other embodiments do not comprise an enlarged section. 
     A distance between a distal end of the lip  14852  and a proximal face of the flange  14832  is equal to or slightly less than a sum of a thickness of the bolster  14840  and the gel pad  10530 . In some embodiments, the gel pad is from about 5 mm (about 0.4 inch) to about 30 mm (about 1.2 inch) thick, or from about 13 mm (about 0.5 inch) to about 25 mm (about 1 inch) thick. 
     The trocar  14800  has at least two configurations: a first or insertion configuration illustrated in  FIG.  14 A , and a second or fixation configuration illustrated in  FIG.  14 B . 
     In an embodiment of a method for using the trocar  14800 , the trocar  14800  is placed in the insertion configuration in which the bolster  14840  is first positioned on the cannula body  14812 . The trocar  14800  is placed in the artificial body wall either before the artificial body wall is coupled to a patient&#39;s body and/or after coupling thereto. 
     In the embodiment illustrated in  FIG.  14 A , the bolster  14840  is positioned at the proximal end of the cannula body  14812 , where the bolster  14840  frictionally engages a distal portion of a cannula bell  14814 , which is an enlarged portion at the proximal end of the cannula  14810  to which the seal assembly  14820  couples. 
     The distal end of the trocar  14800  is positioned on, then the retainer  14830  inserted through an artificial body wall, for example, a gel pad  10530 . In some embodiments, an obturator  13900  ( FIG.  13   ) is first inserted through the seal assembly  14820  at the proximal end of the trocar with the tip  13910  extending from the distal end thereof before this step. In other embodiments, an opening is first made in the artificial body wall using another instrument. In other embodiments, the distal end of the trocar  14800  is forced through the artificial body wall, generating an opening in the process. 
     The trocar  14800  is then converted into the fixation configuration illustrated in  FIG.  14 B  by sliding the bolster  14840  down the cannula body  14812 , and over the lip  14852  onto the enlarged section  14852 . In the illustrated configuration, the artificial body wall is captured and compressed between the flange  14830  of the retainer and the bolster  14840 . The lip  14852  locks the bolster  14840  in place, preventing it from moving proximally, thereby fixing or locking the trocar  14800  to the artificial body wall. 
     In the fixation configuration, the trocar  14800  fixed relative to a local portion of the artificial body wall to which it is engaged. As discussed above, however, embodiments of artificial body walls exhibit high elongations. Accordingly, the trocar  14800  is translatable and/or pivotable relative to an original position and orientation by deforming the artificial body wall. 
     In embodiments using an obturator  13910 , the obturator is withdrawn. The trocar  14800  serves as an access port for one or more instruments during a surgical procedure. 
     If desired, the trocar  14800  is removed from the artificial body wall, for example, by first disengaging the bolster  14840  from the locking component  14850 , then pulling the retainer  14830  from the artificial body wall. In some embodiments, the trocar  14800  and artificial body wall are not disengaged and are disposed of as a unit. In some embodiments, the bolster  14840  is not disengagable from the locking component  14850 . 
       FIG.  15    is a side view of another embodiment of a retention trocar  15000 , which is generally similar to the embodiment illustrated in  FIGS.  14 A and  14 B  and described above. The trocar  15000  comprises an elongate, tubular cannula  15810  comprising a proximal end, a distal end, and a cannula body  15812 ; a seal assembly  15820  coupled to the proximal end of the cannula  15810 ; a retainer  15830  disposed at the distal end of the cannula  15810 ; a bolster  14840  through which the cannula body  15812  extends; and a locking component  15850  disposed on the cannula body proximal of the retainer  15830 . 
     In the illustrated embodiment, the locking component  15850  comprises an enlarged section  15854  on which are disposed screw threads  15852 . The bolster  15840  comprises matching threads. Consequently, the bolster  15840  is threadably engagable to the locking component  15850 . The threading also permits adjusting the relative positions of the bolster  15840  and a flange  15832  of the retainer in the fixation configuration of the trocar  15800 , thereby permitting fixation to an artificial body wall with a non-uniform thickness and/or to artificial body walls of different thicknesses. 
       FIG.  16 A  is a side view of another embodiment of a trocar  16800 .  FIG.  16 B  is a perspective view of an embodiment of a bolster  16840  usable with the trocar  16800 . The combination of the trocar  16800  and bolster  16840  are generally similar to the embodiments of trocars illustrated in  FIGS.  14 A,  14 B, and  15   . The trocar  16800  comprises an elongate, tubular fixation cannula  16810  comprising a proximal end, a distal end, and a cannula body  16812 ; a seal assembly  16820  coupled to the proximal end of the cannula  16810 ; a retainer  16830  disposed at the distal end of the cannula  16810 ; and a locking component  16850  disposed on the cannula body proximal of the retainer  16830 . 
     In the illustrated embodiment, the locking component  16850  comprises an enlarged section  16854  comprising a plurality of annular rings  16852  extending radially from the cannula body  16812 , which define a plurality of annular slots  16856 . In the illustrated embodiment, a proximal edge of each ring  16856  is beveled; however, some embodiments do not comprise a beveled edge. 
       FIG.  16 B  illustrates an embodiment of a bolster  16840  in the form of a clip comprising a flattened body  16842  comprising a cut-out  16844  comprising a semicircular portion. The cut-out  16844  is dimensioned to engage the slots  16856 . A thickness of the body  16842  at the cut-out  16844  is also dimensioned to engage the slots  16856 . The bolster  16840  comprises a grip  16846  extending vertically from the body  16842 , which provides a user grip for installing and/or adjusting the bolster  16840 . In other embodiments, the cut-out  16844  has another shape, for example, polygonal, rectangular, a portion of a hexagon, and the like. 
     In use, the retainer  16830  of the trocar is inserted through an artificial body wall as discussed above, and fixed therein by engaging the bolster  16840  in a slot  16856  providing a desired fixation force. The degree of fixation is adjustable by selecting a different slot. 
     In some embodiments, the bolster cut-out  16844  engages a plurality of slots, thereby providing additional stability in the fixation configuration. Other embodiments comprise a bolster through with the cannula body  16812  extends, similar to the embodiments discussed above. In some of these embodiments, the locking component  16850  serves as a ratchet. The bolster comprises one or more pawls, which are optionally disengagable, thereby enhancing adjustability. 
       FIG.  17 A  illustrates a side view of an embodiment of a trocar  17800  comprising a fixation cannula and  FIG.  17 B  is a perspective view of an embodiment of a bolster. The embodiments illustrated in  FIGS.  17 A and  17 B  are generally similar to the embodiments of trocars illustrated in  FIGS.  14 A- 16 B  and described above. 
     The trocar  17800  comprises an elongate, tubular fixation cannula  17810  comprising a proximal end, a distal end, and a cannula body  17812 ; a seal assembly  17820  coupled to the proximal end of the cannula  17810 ; a retainer  17830  disposed on the cannula body  17812 ; and a locking component  17850  disposed at the distal end of the cannula  17810 . The illustrated embodiment of the trocar  17800  is similar to the embodiment illustrated in  FIG.  16 A  with the positions of the retainer  17830  and the locking component  17850  reversed. In the illustrated embodiment, a flange  17832  of the retainer faces distally. 
     The locking component  17850  comprises an enlarged section  17854  comprising a plurality of annular rings  17852  extending radially from the cannula body  17812 , which define a plurality of annular slots  17856 . 
       FIG.  17 B  illustrates an embodiment of a bolster  17840  in the form of a clip comprising a flattened body  17842  comprising a cut-out  17844  comprising a semicircular portion. The cut-out  17844  is dimensioned to engage slots  17856  in the locking component. A thickness of the body  17842  at the cut-out  17844  is also dimensioned to engage the slots  17856 . The illustrated embodiment of the bolster does not comprise a grip; however, other embodiments comprise a grip. 
     In some embodiments for using the embodiment of the trocar  17800 , the cannula  17810  is fixed to an artificial body wall before the artificial body wall is coupled to a patient&#39;s body. For example, in some embodiments, one or more trocars  17800  are fixed on a gel pad  10530  ( FIG.  10 A ) of a gel cap  10500  before the gel cap  10500  is coupled to a retractor  6100 . 
     While certain embodiments have been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope thereof as defined by the following claims.