Patent Publication Number: US-2023157724-A1

Title: Surgical cannula with removable pressure seal

Description:
CROSS-CITATION OF RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 17/173,531, filed Feb. 11, 2021, and entitled “Surgical Cannula with Removable Pressure Seal,” which claims priority to U.S. Provisional Application No. 62/972,897, filed Feb. 11, 2020, and entitled “Cannula with Removable Pressure Seal.” The entire disclosure of each of the applications mentioned above is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to the field of surgical cannulas that may be temporarily inserted into living tissue. Cannulas may be used during surgery to introduce tools or substrates into a human or animal body. 
     BACKGROUND 
     Surgical cannulas are generally well-known in the art of arthroscopic surgery. For example, various types of cannulas are used to control the inflow or outflow of fluids, to allow access for tools into the tissue, and for other functions. In some types of surgeries, a graft or other substrate material may be introduced into a surgical site. Additionally, many arthroscopic surgeries, such as joint surgeries, use pressurized irrigation fluid to keep tissue separated apart from other tissue. In particular, pressurized irrigation fluid may be used to aid in visualization of the surgical site as well as to prevent bleeding from vasculature surrounding the surgical cuts. Other types of surgeries, such as gastrointestinal procedures, use pressurized gas to provide access to and visualization of the surgical site. 
     Accordingly, there is a need in the art for cannulas that address the need to serve these several functions during an arthroscopic surgery. 
     SUMMARY OF THE DISCLOSURE 
     In one aspect, the disclosure provides a surgical cannula comprising: a seal structure including at least one valve; and a cannula body, including: an insertion portion having a distal opening that is configured to be inserted into tissue, and a receiving portion that includes a proximal opening and is configured to reversibly receive the seal structure; wherein the seal structure is configured to removably associate with the proximal opening of the cannula body; and wherein the seal structure is configured to retain a positive pressure within the cannula body when engaged with the cannula body, and the seal structure is configured to retain a positive pressure within the cannula body when an object is inserted through the cannula and the seal structure. 
     In another aspect, the disclosure provides a surgical cannula comprising: a seal structure including a first valve and a second valve; and a cannula body, including: an insertion portion that includes a distal opening and is configured to be inserted into tissue, and a receiving portion that includes a proximal opening and is configured to reversibly receive the seal structure; wherein the seal structure reversibly covers the proximal opening of the cannula body; wherein the seal structure is configured to retain a positive pressure within the cannula body when an object is inserted through the cannula. 
     In another aspect, this disclosure provides a surgical cannula comprising: a seal structure including at least one valve; and a cannula body, including an insertion portion that includes a distal opening and is configured to be inserted into tissue, and a receiving portion that includes a proximal opening and is configured to reversibly receive the seal structure; wherein the seal structure is configured to retain a positive pressure within the cannula body when an object is inserted through the cannula and the seal structure; and wherein the cannula body further includes one or more suture attachment structures configured to hold a suture so as to anchor the cannula to tissue into which the insertion portion has been inserted. 
     Other systems, methods, features, and advantages of the disclosure will be, or will become, apparent to one of ordinary skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description and this summary, be within the scope of the disclosure, and be protected by the following claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts throughout the different views. 
         FIG.  1    is a perspective top view of a first embodiment of a surgical cannula in accordance with this disclosure; 
         FIG.  2    is a perspective cross-sectional view of the first embodiment of a surgical cannula in accordance with this disclosure; 
         FIG.  3    is a perspective bottom view of the first embodiment of a surgical cannula in accordance with this disclosure; 
         FIG.  4    is a cross-sectional view of a first surgical procedure that involves the use of a surgical cannula in accordance with this disclosure; 
         FIG.  5    is a perspective view of the first embodiment of a surgical cannula with the removable top separated from the cannula body; 
         FIG.  6    is another perspective view of the surgical cannula with the removable top separated from the cannula body; 
         FIG.  7    is a cross-sectional view of a second surgical procedure that involves the use of a surgical cannula in accordance with this disclosure; 
         FIG.  8    is a perspective top view of a second embodiment of a surgical cannula in accordance with this disclosure; 
         FIG.  9    is an exploded view of the several subcomponents making up the second embodiment of a surgical cannula in accordance with this disclosure; 
         FIG.  10    is a perspective top view of the second embodiment of a surgical cannula with the removable top secured to the cannula; 
         FIG.  11    is a perspective bottom view of the second embodiment of a surgical cannula with the removable top secured to the cannula; 
         FIG.  12    is a first perspective cross-sectional view of the second embodiment of a surgical cannula in accordance with this disclosure; 
         FIG.  13    is a second perspective cross-sectional view of the second embodiment of a surgical cannula in accordance with this disclosure; 
         FIG.  14    is a perspective top view of a third embodiment of a surgical cannula in accordance with this disclosure; 
         FIG.  15    is a side view of the third embodiment of a surgical cannula in accordance with this disclosure; 
         FIG.  16    is a first side exploded view of the several subcomponents of the third embodiment of a surgical cannula in accordance with this disclosure; 
         FIG.  17    is a second side exploded view of the several subcomponents of the third embodiment of a surgical cannula in accordance with this disclosure, and a tool used in conjunction with the cannula; 
         FIG.  18    is a cross-sectional view of the third embodiment of a surgical cannula in accordance with this disclosure; 
         FIG.  19    is a perspective top view of a fourth embodiment of a surgical cannula in accordance with this disclosure; 
         FIG.  20    is a cross-sectional view of the fourth embodiment of a surgical cannula in accordance with this disclosure; 
         FIG.  21    is a perspective bottom view of the fourth embodiment of a surgical cannula in accordance with this disclosure; 
         FIG.  22    is an perspective cross-sectional view of the fourth embodiment of a surgical cannula in accordance with this disclosure; 
         FIG.  23    is a perspective view of a fifth embodiment of a surgical cannula in accordance with this disclosure; 
         FIG.  24    is a perspective view of the fifth embodiment of a surgical cannula with a tool therein; 
         FIG.  25    is a perspective cross-sectional view of the fifth embodiment of a surgical cannula with the tool therein; 
         FIG.  26    is a second perspective cross-sectional view of the fifth embodiment of a surgical cannula with the tool therein; 
         FIG.  27    is a perspective view of the fifth embodiment of a surgical cannula with the seal structure removed from the receiving portion of the cannula body; 
         FIG.  28    is a top perspective view of the fifth embodiment of a surgical cannula with the seal structure and tether entirely removed from the cannula body; and 
         FIG.  29    is a cross-sectional perspective view of the fifth embodiment of a surgical cannula with the seal structure removed from the cannula body. 
     
    
    
     DETAILED DESCRIPTION 
     Broadly disclosed are surgical cannulas that include a removable seal structure that retains pressure inside the cannula. Such a cannula may be used during arthroscopic surgery to both provide an inlet for arthroscopic tools, and also act as a port to allow introduction of a graft substrate into the surgical site. 
     Generally, a cannula may broadly refer to a tube that can be inserted into the body, and used for the delivery or extraction of fluid or other materials. Surgical cannulas may generally include intravenous cannulas, nasal cannulas, or surgical cannulas. 
     In particular, this disclosure is directed to surgical cannulas that may retain pressurized fluid (liquid or gas) within a surgical site when a seal structure is engaged on the cannula, while also allowing removal of the seal structure in order to permit larger items, such as tissue grafts, to be introduced through the cannula. 
     For example,  FIG.  1    shows a first embodiment of a cannula in accordance with this disclosure. Cannula  100  may include cannula body portion  102  that includes an insertion portion  120 , a receiving portion  128 , and a taper portion  126  between the two. Insertion portion  120  may include a distal opening  124  in the cannula. Insertion portion  120  may be configured to be inserted into tissue, such as a human body or an animal body, and may be generally cylindrical in shape. Insertion portion  120  may also include threads  122  on an exterior surface thereof. 
     Threads  122  may secure cannula  100  in the tissue, and may allow more accurate placement of the cannula  100  within the tissue by allowing a user to increase or decrease the depth to which the cannula is inserted into the tissue by rotating the cannula  100 . 
     Cannula  100  may also include a seal structure  104 . Seal structure  104  may engage with receiving portion  128 . Seal structure  104  may include a valve  106 . In some embodiments, valve  106  may be a tricuspid valve, as shown in  FIG.  1   . A tricuspid valve, as is generally known in the art, is a one-way valve made up of three flaps that come together at a single point. Valve  106  may therefore retain fluidic pressure inside cannula body  102  when cannula  100  is used in a surgical procedure. 
     Seal structure  104  may also include top portion  108  and side portion  110 . Finally, seal structure  104  may also include tether  114  that may connect seal structure  104  to cannula body portion  102  when seal structure is not engaged with receiving portion  128 . 
       FIG.  2    shows cannula  100  in further detail.  FIG.  2    shows a cross-sectional view of cannula  100 . As shown in this view, cannula body  102  may be hollow so as to allow passage of tools or tissue through the cannula  100  from a proximal end to a distal end  124 . Namely, insertion portion  120  of cannula body  102  may be a hollow cylinder of a first gauge (diameter), receiving portion  128  of cannula body  102  may be a hollow cylinder of a second gauge (diameter) that is larger than the first gauge, and taper portion  126  may taper in gauge between the two. 
     Seal structure  104  may also include side portion  110  that engages with lip  129  on cannula body portion  102  to engage a seal between seal structure  104  and cannula body portion  102 . Lip  129  may cause seal structure  104  to be securely, but reversibly, retained against cannula body portion  102 . 
     In the embodiment shown in  FIG.  2   , seal structure  104  may include first valve  106  and also second valve  107 . The use of two such valves may even better ensure that pressure is retained inside cannula  100  during surgical use. In some embodiments, first valve  106  may be a tricuspid valve and second valve  107  may also be a tricuspid valve, as shown in  FIG.  2   . In some embodiments, other types of valves may be used. Other embodiments discussed herein utilize duckbill valves. In some cases, such a duckbill valve may be utilized in the embodiment shown in  FIGS.  1 - 7    (e.g., substituted for one or both of the tricuspid valves). 
     First valve  106  and second valve  107  may be separated by a void  109  defined by seal sidewalls  105 . Void  109  may catch any seepage of a pressurized fluid from taper portion  126  and insertion portion  120  that escapes past second valve  107 , while first valve  106  may still ensure no liquid escapes to outside of the cannula. 
       FIG.  2    also shows tether  114  in greater detail. Namely, tether  114  may include arm portion  116  that connects to top portion  108  of seal structure  104  at one end of arm portion  116 . Arm portion  116  may then connect to ring portion  118  that encircles one end of insertion portion  120  of the cannula body  102 . In this way, tether  114  may connect seal structure  104  to cannula body portion  102  even when seal structure  104  is not engaged with receiving portion  126 . 
     Also as shown in  FIG.  2   , seal structure  104  may be a continuous unitary piece of a single material. In some embodiments, seal structure  104  may be made of continuous silicone material. 
       FIG.  3    shows cannula  100  from a perspective bottom view. In this view,  FIG.  3    shows how cannula  100  looks when seal structure  104  is engaged with receiving portion  128 . Namely, second valve  107  is adjacent to taper portion  126  so as to retain any pressurized fluid within a surgical site that may flow upward into insertion portion  120  and taper portion  126 . 
     Also shown in  FIG.  3    is tab portion  112  that may be connected to side portion  110  of top portion  108  of seal structure  104 . Tab portion  112  may allow a user to easily and conveniently remove seal structure  104  from engagement with cannula body portion  102 . For example, a surgeon may remove seal structure  104  from cannula body portion  102  by grasping tab  112  and pulling on tab  112  until side portion  110  no longer engages with lip  129  (see  FIG.  2    for connection between side portion  110  and lip  129 ). 
       FIG.  4    shows one example of how a cannula in accordance with this disclosure may be used during a surgical procedure. In the embodiment shown in  FIG.  4   , a surgeon  202  may operate a tool  204  that is inserted through cannula  100 , which has been inserted into a patient  208  at surgical site  206 . Accordingly, this disclosure also provides methods of performing arthroscopic surgery using the cannula devices disclosed herein. 
     The cross section of surgical site  206  shown in  FIG.  4    shows how the cannula is used during a surgical procedure in greater detail. Namely, insertion portion  120  of cannula  100  may be partially implanted into the patient&#39;s tissue using threads  122 . Cannula  100  may be introduced into the tissue by first making an incision  220  into skin tissue  210  and muscle tissue  212  such that distal end  124  will be located adjacent to the desired surgical site  226 . In the embodiment shown, the surgical procedure may be a rotator cuff surgery. In this embodiment, desired surgical site  226  may be where rotator cuff muscle and ligaments  216  attach to the humoral head  218  at the subacromial space. 
     In order to perform such a surgery, a pressurized liquid  214  may be used to inflate and visualize the surgical site  226 . Pressurized liquid  214  may be clear saline, for example. Also referred to as an irrigation fluid, pressurized liquid  214  may be an isotonic solution that is used to enable visualization and also prevent bleeding from vasculature surrounding the surgical site  226 . Pressurized liquid  214  may be at a pressure of around 20-30 mmHg. In some cases, debris or blood may cloud the pressurized fluid. In such cases, the pressurized fluid may be flushed. In doing so, the pressure and flow of the fluid may be raised significantly. Accordingly, in order to withstand such elevated pressures, in some embodiments, the disclosed seal of the cannula may be configured to sustain pressures up to about 140 mmHg. 
     Cannula  100  may allow surgeon  202  to introduce tool  204  into the surgical site  226  while retaining fluid  214  under pressurization. Tool  204  may include tool shaft  222  that extends through cannula  100  and ends at tool tip  224 . Namely, tool shaft  222  may extend through first valve  106  and second valve  107  which conform around tool shaft  222  such that pressurization  230  of the pressurized liquid  214  is contained within the surgical site  226  as well as within the insertion portion  120  and taper portion  126  of cannula  100 . In this way, seal structure  104  may be configured to retain a positive pressure  230  within the cannula body when a tool  204  is inserted through the cannula  100 . 
       FIG.  5    next shows cannula  100  when seal structure  104  is not engaged with cannula body portion  102 . As mentioned, tether  114  may keep seal structure  104  attached to cannula body portion  102  even when seal structure  104  is not engaged with body portion  102 . Also shown in  FIG.  5    is proximal opening  125  in receiving portion  128  that is located opposite distal opening  124  in insertion portion  120 . Proximal opening  125  may be surrounded by lip  129 , which engages with side portion  110  of seal structure  104 , as mentioned above. Seal structure  104  may therefore cover proximal opening  125  when seal structure  104  is engaged with cannula body portion  102 . 
     The embodiment in  FIG.  5    may also include ridges  130 ,  132  on seal sidewalls  105  that further ensure a tight (but reversible) fit between seal structure  104  and receiving portion  128 . As shown in  FIGS.  2 ,  3 , and  5   , in this embodiment, seal sidewalls  105  engage with an interior surface of receiving portion  128 . Ridges  130 ,  132  may therefore abut interior surface of receiving portion  128  in order to form a seal that retains pressure. 
       FIG.  6    shows the embodiment of  FIG.  5    from another angle, in order to show additional details of seal structure  104 . Namely, second valve  107  may be disposed on a bottom side of seal structure  104  such that second valve  107  may be inserted into receiving portion  128  so as to be located at the most distal end of receiving portion  128 . 
     Also shown in  FIG.  6    is tether  114 . Tether  114  may include arm portion  116  that connects seal structure side portion  110  with ring portion  118 . Ring portion  118  may encircle cannula body  104  at a nearest end of insertion portion  120 . 
     Thus, as shown in  FIGS.  5  and  6   , seal structure  104  may be reversibly engaged with cannula body portion  102  and thus may be removed after engagement with cannula body portion  102 . 
       FIG.  7    shows another surgical procedure  300 , and how cannula  100  may be used when the seal structure is removed from the cannula body portion. Namely, in this embodiment, surgeon  302  may perform surgery on a patient  308  at the patient&#39;s knee  306  through an insertion  320  in the patient&#39;s skin  210  and through tissue  312  surrounding the surgical site. At the stage of the surgery shown, a graft substrate  340  is ready to be introduced into the surgical site  326 . This would typically occur after a surgical site  226 / 326  has been prepared through one or more steps involving the use of tools at the surgical site as shown in  FIG.  4   . In this way, a method of performing arthroscopic surgery in accordance with this disclosure may include delivering a sheet-like implant  340  through the cannula  100  to the surgical site, and securing the sheet-like implant  340  to tissue  316  at the surgical site  326 . 
     In the stage of surgery shown in  FIG.  7   , pressurized liquid  314  is in fluidic communication with the entire interior of cannula  100 . Namely, because seal structure  104  has been removed, pressurized liquid  314  may expand up into insertion portion  120 , taper portion  126 , and receiving portion  128  as shown. Tool  304  may then be attached to proximal opening  125  of cannula  100  and used to introduce graft sheet-life substrate  340  into the interior of the cannula  100  and allow graft substrate  340  to travel down the length of cannula  100  to surgical site  326  along path  342 . Tool  304  may include aspects for maintaining pressurized liquid  314  under pressure  330  during this surgical step. For example, tool  304  may include one or more sealing structures on the shaft of tool  304 . Such sealing structures may seal the cannula during the insertion of the graft. 
     In this way, cannula  100  may be configured so as to allow a graft substrate  340  to travel through it. Namely, cannula  100  may be of sufficient size to allow graft substrate  340  to fit therein. The gauge of the various cannula sections may differ depending on the size of the patient and the type of surgery for which it is used. In addition, the relative proportions of the gauges of the different portions of the cannula may differ. 
     However, in particular embodiments, the second gauge of receiving portion  128  being larger than the first gauge of insertion portion  120  may advantageously help the sheet-like graft substrate  340  (and any supporting structures that may aid in the place of the graft substrate  340 ) roll itself up as it passes along cannula body portion  102  from proximal opening  125  to distal opening  124 . Namely, the shape of taper portion  126  may cause the graft substrate  340  to roll up—and thereby assume a configuration that is advantageous for placement for attachment to the patient&#39;s tissue  316   t . The relative size of the gauges of the various sections of cannula body portion  102  may therefore advantageously aid in the accomplishment of the purpose for which the cannula  100  is to be used. 
     Subsequently, after the graft substrate  340  is successfully inserted, seal structure  104  may be re-engaged with cannula body portion. Then, surgical tools may again be introduced into the surgical site (in order to manipulate the graft substrate  340  and attached it where needed) as shown in  FIG.  4   . In this way, a single surgical cannula  100  may both allow for the introduction of tools into a surgical site under a pressurized liquid, and also allow introduction of a graft substrate into the surgical site. 
       FIG.  8    shows a second embodiment of a cannula  400  in accordance with this disclosure. Cannula  400  may include some features that are substantially similar to features in the first embodiment of cannula  100  discussed above. Namely, cannula  400  may include cannula body portion  402  that includes insertion portion  420  and receiving portion  428 . Insertion portion  420  may include distal opening  424  and threads  422 . Receiving portion  428  may include proximal opening  425 . Cannula  400  may also include seal structure  404 . Seal structure  404  may include side surface  410 , first valve  406 , and housing cover  408 . 
     In the particular embodiment shown in  FIG.  8   , cannula  400  may also include first wing structure  440  and second wing structure  442 . Each of first wing structure  440  and second wing structure  442  may extend laterally outward from cannula body  402  and upward so as to latch onto housing cover  408 . Namely, housing cover  408  may include first notch  444  that is configured to receive first wing structure  440 . Housing cover  408  may also include second notch  446  that is configured to receive second wing structure  442 . 
     Additionally, first wing structure  440  and second wing structure  442  may also act as suture attachment structures. Namely, during surgery a user may choose to anchor cannula  400  to the tissue through which it is inserted by suturing one or more suture attachment structures to the tissue. Namely, sewing a thread of suture  441  around the suture attachment structure and through the tissue such that the suture holds the cannula  400  in place. In this way, a cannula  400  in accordance with this disclosure may include one or more suture attachment structures that may be configured to hold a suture so as to anchor the cannula to the tissue into which the insertion portion  420  of the cannula  400  has been inserted. 
       FIG.  9    shows an exploded view of the several components that may make up cannula  400 . Namely, cannula  400  may include: cannula body portion  402  that includes first wing structure  440  and second wing structure  442 , lower housing portion  450 , a first attachment screw  456 , a second attachment screw  458 , first valve  406 , a second valve  407 , and housing cover  408 . 
     In this particular embodiment, lower housing portion  450  may include seal side surface  410 , first flange hole  452 , and second flange hole  454 . 
     First valve  406  may be a tricuspid valve as discussed with respect to other embodiments above. 
     Second valve  407  may, in some embodiments, be a duckbill valve. A duckbill valve, as is generally known, is a type of one-way valve that has two “lips”  462  in the shape of a duck&#39;s bill that come together to form a seal. Generally, the two lips in a duckbill valve may bend open when pressure is applied from one direction, but not from the other. Duckbill valves may therefore act as a self-contained check valve. Second valve  407  may also include rim portion  460  that may allow second valve  407  to be held in place between lower housing portion  450  and housing cover  408 . 
     Housing cover  408  may include: first cover hole  466 , second cover hole  468 , first notch  444 , second notch  446 , and access hole  464 . First cover hole  466  and second cover hole  468  may be located on opposite sides of housing cover from each other, as may be first notch  444  and second notch  446 . First cover hole  466  may be adjacent to first notch  444 , and second cover hole  468  may be adjacent to second notch  446 . 
     Additionally, first attachment screw  456  and second attachment screw  458  may secure lower housing portion  450  to housing cover  408 , in such a way that first valve  406  and second valve  407  are contained therein. Namely, first attachment screw  456  may extend through first flange hole  452  on lower housing portion  450  into first cover hole  466  in housing cover  408 . Similarly, second attachment screw  458  may extend through second flange hole  454  on lower housing portion  450  into second cover hole  468  in housing cover  408 . 
     In other embodiments, lower housing portion  450  and housing cover  408  may be attached to each other by attachment means other than screws, such as ultrasonic welding or other types of thermal bonding, adhesive, or any other suitable fixation modality. 
       FIG.  10    shows another view of cannula  400 . In this view, seal structure  404  is engaged with cannula body  402 . In this configuration, seal structure  404  is latched into place by first wing structure  440  and second wing structure  442 . Namely, first wing structure  440  may include first diagonal portion  470  that extends outward from cannula body  402  and upwards towards proximal opening  425  (note: proximal opening  425  is covered by seal structure  404  in  FIG.  10   ), first vertical portion  472  that extends upward toward proximal opening  425 , and first latch portion  474  that engages first notch  444  on housing cover  408 . Second wing structure  442  may similarly include second diagonal portion  476 , second vertical portion  478 , and second latch portion  480  that engages with second notch  446  on housing cover  408 . First wing structure  440  and second wing structure  442  may be disposed on opposite sides of cannula body  402 . 
     When seal structure  404  is engaged with cannula body  402 , side surface  410  may be located on the outside of receiving portion  428  of cannula body  402  and surround it. 
       FIG.  11    shows a bottom isometric view of cannula  400  when seal structure  404  is engaged with receiving portion  428  of cannula body  402 . This view further shows how first attachment screw  456  and second attachment screw  458  may secure lower housing portion  450  to housing cover  408 . 
       FIG.  12    is a cross-sectional view of cannula  400 . This cross-sectional view shows additional details of an embodiment where first attachment screw  456  and second attachment screw  458  extend upward through first flange hole  452  and second flange hole  454 , and into first cover hole  466  and second cover hole  468 . As a result, lower housing portion  450  and housing cover  408  hold first valve  406  and second valve  407  in place. Also shown is void  409  between first valve  406  and second valve  407 . 
     In particular,  FIG.  12    further shows how first wing structure  440  and second wing structure  442  reversibly hold seal structure  404  in place. Namely, first wing structure  440  and second wing structure  442  are semi-rigid, and are biased into a position that hold latch portions  474 ,  480  into notches  444 ,  446  when seal structure  404  is engaged onto cannula body  402 . However, first wing structure  440  and second wing structure  442  may be partially flexible in an outward lateral direction as shown by arrows, that allows latch portions  474 ,  480  to slide off of notches  444 ,  446 . In this way, seal structure  404  may be disengaged and removed from cannula body  402  in an alternative manner. First wing structure  440  and second wing structure  442  may be configured such that a surgeon may disengage seal structure  404  with an outward motion of a thumb and forefinger, thereby allowing ease of use during surgery. Non-rotational disengagement may be preferred in some situations, for example where an instrument remains inserted through the cannula. 
     Next,  FIG.  13    shows a cross-sectional view with further structure of second valve  407 . Namely, second valve  407  may be a duckbill valve that includes void  409  between second valve  407  and first valve  406 . Second valve  407  may include first lip  490  and second lip  492  that come together at seam  494 . When pressure is exerted on second valve  407  downward from the direction of first valve  406 , first lip  490  and second lip  492  may part from each other as shown by the arrows in  FIG.  13   . However, in contrast, pressure exerted on second valve  407  upward from the direction of insertion portion  420  and distal opening  424  will not cause lips  490 ,  492  to part. Therefore, pressurized liquid will be retained within cannula body  402 . 
     It will be noted that the embodiment shown in  FIGS.  8 - 13    may also include a tether, such as shown and discussed with respect to the embodiment shown in  FIGS.  1 - 7   . 
       FIG.  14    shows a third embodiment of a cannula  500  in accordance with this disclosure. Cannula  500  shares many features with cannula  400  as discussed above, but also differs with respect to several features. Namely, cannula  500  includes first suture attachment flange  540  including first eyelet  541  and second suture attachment flange  542  including second eyelet  543 . First suture attachment flange  540  and second suture attachment flange  542  may be located on taper section  526  of cannula body  502 , between insertion portion  520  and receiving portion  528 . Flanges  540 ,  542  may extend laterally outward from cannula body  502 . As discussed above with respect to first wing structure  440  and second wing structure  442 , flanges  540 ,  542  may be used to anchor cannula  500  to tissue at an incision site by passing a thread of suture through one or more of eyelets  541 ,  542  and also through the skin proximate to the incision site. 
     Cannula  500  may also include retaining protrusion  591  on a side  510  of retaining portion  528 . Retaining protrusion  591  may be used to retain seal structure  504  on cannula body  502 . Namely, seal structure may include vertical cutout  593  and horizontal cutout  593 . Retaining protrusion  591  may have a width that is the same as a width of vertical cutout  593 , and retaining protrusion  591  may have a height that is the same as a height of horizontal cutout  595 . In this way, retaining protrusion  591  may be moved along vertical cutout  593  when cannula body  502  and seal structure  504  are brought together. Then, retaining protrusion  591  may be moved along horizontal cutout  595  by rotating seal structure  504  as shown by the arrow in  FIG.  14   . In this way, retaining protrusion  591  may keep seal assembly  504  removably engaged with the receiving portion  528  of cannula body  502 . 
       FIG.  15    further shows features of cannula  500 . Namely, in  FIG.  15   , seal structure  504  is engaged with cannula body  502  by the disposition of retaining protrusion  591  within horizontal cutout  595 . Seal structure  504  may be rotated clockwise or counterclockwise in order to move retaining protrusion  591  within horizontal cutout  595 , so as to disengage seal structure  504  from cannula body  502 . 
       FIG.  16    shows an exploded view of the several subcomponents that may make up cannula  500 . Namely, cannula  500  may include: cannula body  502  that may include retaining protrusion  591 , lower housing portion  550  that may include vertical cutout  593  and horizontal cutout  595 , first valve  506  which may be a tricuspid valve, second valve  507  which may be a duckbill valve, and housing cover  508 . 
       FIG.  17    shows an exploded view of the several subcomponents that may make up cannula  500 , and also a tool  600 . Tool  600  may be used during a surgical procedure, such as shown in  FIG.  4   , in conjunction with cannula  500 . Namely, tool  600  may extend through first valve  506  and second valve  507  so as to reach a surgical site inside a body. First valve  506  and second valve  507  may retain a pressure seal against tool  600 , such that pressurized surgical irrigation fluid may be retained within the surgical site while tool  600  is being used. Tool  600  is illustrated as an obturator. However, it will be noted that any of various types of elongate tools may be utilized with the disclosed cannulas. For example, probes, grasps, and other tools including long shafts against which the disclosed valves may seal may be utilized with the disclosed cannulas. 
     Next,  FIG.  18    shows a cross-sectional view of cannula  500 . This view shows how cannula  500  may include first retaining protrusion  591  and also second retaining protrusion  597 . First retaining protrusion  591  may align with first vertical cutout  593  and first horizontal cutout  595  as discussed, while second retaining protrusion  597  may align with second vertical cutout  599  and second horizontal cutout (not shown in  FIG.  18   ). 
     First retaining protrusion  591  and second retaining protrusion  597  may be located on opposite sides of cannula body  502  from each other. In this way, the two retaining protrusions  591 ,  597  may ensure a snug and tight fit between cannula body  502  and seal structure  504  that retains pressurized surgical liquid. 
     It will be noted that the embodiment shown in  FIGS.  14 - 18    may also include a tether, such as shown and discussed with respect to the embodiment shown in  FIGS.  1 - 7   . 
     A fourth embodiment of a surgical cannula in accordance with this disclosure is shown in  FIGS.  19 - 22   . Namely, as shown in at least  FIG.  19   , surgical cannula  700  may include a cannula body  702  and a seal structure  704 . Cannula body  702  may be substantially similar to cannula body  102 , cannula body  402 , and cannula body  502  as discussed above, in some respects. However, in other aspects, cannula body  702  may differ from other embodiments disclosed herein, as discussed below. 
     In particular, cannula body  702  may include insertion portion  720 , receiving portion  728 , and taper portion  726  between insertion portion  720  and receiving portion  728 . Insertion portion  720  may be configured to be inserted into tissue, such as a human body or an animal body, and may be generally cylindrical in shape. Insertion portion  720  may also include threads  722  on an exterior surface thereof. Taper portion  726  may be configured to roll up a graft upon insertion through the cannula, as described above. 
     Cannula body  702  may also include first suture attachment flange  740  including first eyelet  741  and second suture attachment flange  742  including second eyelet  743 . First suture attachment flange  740  and second suture attachment flange  742  may be located on taper section  726  of cannula body  702 , between insertion portion  720  and receiving portion  728 , on laterally opposite sides of cannula body  702  from each other. Flanges  740 ,  742  may extend laterally outward from cannula body  702 . As discussed above, flanges  740 ,  742  may be used to anchor cannula  700  to tissue at an incision site by passing a thread of suture through one or more of eyelets  741 ,  742  and also through the skin of the patient proximate the cannula insertion site. 
       FIG.  19    also shows various details of seal structure  704 . In particular, seal structure  704  may include a through-hole  706  on a top surface  708 . Through-hole  706  may have a first diameter that is sufficiently large as to allow a tool such as obturator tool  600  (shown in  FIG.  17   ) to pass through and enter into the cannula  700 . For example, in some embodiments, seal structure  704  may be made from an elastomeric material—such that through-hole  706  first diameter may be smaller than the diameter of a tool  600  and yet also stretch to expand to allow tool  600  into the cannula  700 . In this embodiment, top surface  708  may press against tool  600  when it is inserted into through-hole  706  so as to form a seal around tool  600 . This may advantageously allow seal structure  704  to retain pressure within cannula  700  during use. 
     Seal structure  704  may also include tab portion  712 . Tab portion  712  may be connected to side portion  710  of seal structure  704 . Tab portion  712  may allow a user to easily and conveniently remove seal structure  704  from engagement with cannula body portion  702  by grasping onto tab portion  712 . 
     Seal structure  704  may also include tether  714 . Tether  714  may connect seal structure  704  to cannula body portion  702  when seal structure  704  is not engaged with receiving portion  728 . Namely, when a user such as a surgeon removes seal structure  704  from cannula body portion  702  during use, tether  714  may ensure that seal structure  704  is not lost or otherwise distantly separated. Tether  714  may include ring  718  and arm  716 . Tether ring  718  may be configured to surround insertion portion  720  of cannula body  702 . Tether arm  716  may have sufficient length to allow seal structure  704  to be removed from cannula body  702  and located out of the way of a surgical procedure, when needed. 
       FIG.  20    shows a cross-sectional view of the fourth embodiment of a surgical cannula  700 . This view shows how cannula body portion  702  may include threads  722  that wrap around insertion portion  720 , how first suture attachment flange  740  and second suture attachment flange  742  may be disposed on opposite sides of taper portion  726  from each other, and how receiving portion  728  may include several structures configured to engage with seal structure  704 . 
     In particular, receiving portion  728  of cannula body  702  may include a first retaining lip  732 . First retaining lip  732  may be located adjacent to proximal opening  723  of cannula body  702 . First retaining lip  732  may also include a sloped top surface  734 . Sloped top surface  734  may therefore result in first retaining lip  732  gradually increasing in width, as measured outward laterally from cannula body portion  702 . Receiving portion  728  may also include a second retaining lip  736  that also extends outward laterally from receiving portion  728  of cannula body portion  702 . Second retaining lip may be located closer to distal opening  724  than first retaining lip  732 . First retaining lip  732  and second retaining lip  736  may be located a small distance apart from each other, so as to form a retaining groove  738  between them. 
     This configuration of first retaining lip  732 , retaining groove  738 , and second retaining lip  736  may allow seal structure  704  to reversibly engage with cannula body portion  702  in such a way as to retain pressure within the surgical cannula  700  when in use. Specifically, seal structure  704  may include a retaining hook structure  730  that extends laterally inward from a sidewall  710  of the seal structure  704 . In particular, retaining hook structure  730  may extend laterally inward from an inner surface  711  of sidewall  710 . In this way, retaining hook structure  730  may slide past first retaining lip  732 , and become lodged in retaining groove  738  between first retaining lip  732  and second retaining lip  736  when engaged. In some embodiments, seal structure  704  may be comprised of an elastomeric material that bends or stretches within some range—and in such embodiments, sidewall  710  may flex laterally outward so as to allow retaining hook structure  730  to slide along top surface  734  of first retaining lip  732  so as to become reversibly engaged in retaining groove  738 . In some embodiments, seal structure  704  may be configured such that retaining hook structure  730  extends below second retaining lip  736 . In such configurations, having the two retaining lips may provide two separate seals with the inner surface  711  of seal structure  704 . 
       FIG.  20    also shows how, in this embodiment, seal structure  704  may further include a tricuspid valve  707 . Tricuspid valve  707  may be located in line with through-hole  706 , so that a tool  600  may be inserted through both tricuspid valve  707  and through-hole  706  when cannula  700  is being used in a surgical procedure. Specifically, seal structure  704  may include a cavity  709  that is created by top surface  708 , cavity sidewall  705 , and bottom surface  717 . Cavity  709  may be configured to retain pressure therein, and catch any seepage of a pressurized fluid that may come through tricuspid valve  707  when the cannula  700  is in use. 
     In some embodiments, tricuspid valve  707  may have a second diameter that is larger than first diameter of through-hole  706 . Tricuspid valve  707  may therefore allow a tool  600  to maneuver with some degree of lateral movement while inserted through surgical cannula  700 , as shown in  FIG.  4    and discussed above. In this way, smaller first diameter of through-hole  706  may ensure an at least partial seal against tool  600  while valve  707  (having larger second diameter) may create a second seal against the tool while still allowing the tool necessary movement. As a result, through-hole  706  and valve  707  may collectively ensure that pressure is retained within cannula  700  when in use. 
     Next,  FIG.  21    shows a perspective bottom view of seal structure  704 . Specifically,  FIG.  21    shows additional details of the underside of the seal structure  704  and the related structures that allow seal structure  704  to reversibly engage with cannula body portion  702  ( FIG.  20   ). Namely, as shown in  FIG.  21   , seal structure  704  may include tricuspid valve  707  on bottom surface  717 . Tricuspid valve  707  may therefore extend downward into receiving portion  728 , such that cavity sidewall  705  may be adjacent to an inner surface of receiving portion  728  (as shown in  FIG.  20   ). Receiving portion  728  may therefore be contained within opening  713 , that is created between inner surface  711  of sidewall  710  and cavity sidewall  705 . 
     In some embodiments, as shown in  FIG.  21   , the seal structure  704  may be formed of a continuous unitary piece material. In some particular embodiments, seal structure  704  may be a unibody continuous piece of an elastomeric material. 
     Also shown in  FIG.  21    is retaining hook structure  730 —and how retaining hook structure  730  extends circumferentially around a bottom perimeter of sidewall  710 . In such embodiments, retaining hook structure  730  may therefore form a continuous seal around the entirety of receiving portion  728  of cannula body portion  702 . This may advantageously allow seal structure  704  to retain pressure therein when in use in a surgical procedure. 
       FIG.  22    shows a perspective cross-sectional view of cannula body portion  702 . In this view, additional details of first retaining lip  732  and second retaining lip  736  are shown. Specifically, first retaining lip  732  extends circumferentially around receiving portion  728 . Second retaining lip  736  may also similarly extend circumferentially around receiving portion  728 . In this way, retaining groove  738  may extend around the entire circumference of cannula body portion  702  so as to allow retaining hook structure  730  to set therein. Again, as described above, in some embodiments, retaining hook structure  730  may be disposed distally of second retaining lip  736  when the seal structure is engaged with cannula body portion  702 . 
     Additionally,  FIG.  22    shows cannula receiving portion  728  top surface  731 . Top surface  731  may, in accordance with  FIG.  20   , rest against inner surface  715  (see  FIG.  21   ) of seal structure  704  so as to further ensure a proper seal is created between cannula body portion  702  and seal structure  704 . 
     Next, a fifth embodiment of a surgical cannula is shown in  FIGS.  23 - 29   .  FIG.  23    shows a perspective view of a surgical cannula  800 . Surgical cannula  800  may include various features having similarities with the other embodiments of surgical cannulas discussed herein. 
     Specifically, surgical cannula  800  may include a cannula body  802  and a seal structure  804 . Seal structure  804  may include tether  814 , that includes tether ring  818 , and tab portion  812 . In this embodiment, seal structure  804  may include through-hole  806  on top surface  808 . Through-hole  806  may have a larger diameter than e.g. through-hole  706  in order to accommodate different types of surgical tools. In some embodiments, diameter of through-hole  806  may be at least 50% of a diameter of top surface  808 . Within through-hole  806 , valve  807  is contained inside seal structure  804 . 
     Cannula body  802  may include threads  822  on an outer surface thereof, as shown. Cannula body  802  may also include distal opening  824  disposed opposite through-hole  806 . Additionally, cannula body  802  may include first suture attachment flange  840  (with first eyelet  841  therein) and second suture attachment flange  842  (with second eyelet  843  therein). 
       FIG.  24    is a perspective view of the fifth embodiment of a surgical cannula  800  with a tool  900  therein. As shown in  FIG.  24   , tool  900  may be an obturator. However, it will be understood that any various types of elongated instruments may be inserted through cannula  800 . Tool  900  may be inserted into through-hole  806 , extend along cannula body  802 , and a portion  906  of tool  900  may extend out of distal opening  824 . Tool handle  902  may abut top surface  808  of seal structure  804  on surgical cannula  800 . In this way, tool  900  may be used during a surgical procedure by being inserted into surgical cannula  800 . For example, cannula  800  may be inserted through tissue using tool (obturator)  900  to facilitate the piercing of the tissue. 
       FIG.  25    is a perspective cross-sectional view of tool  900  as inserted into surgical cannula  800 . Namely, tool  900  shaft  904  may extend in through-hole  806 , and through valve  807  such that valve  807  forms a seal around tool shaft  904 . In this way, valve  807  may separate fluid contained within cannula body  802  during a surgical procedure from an outer area  809  exposed to outside air. Additionally,  FIG.  25    also shows how in some embodiments the width of cannula body may vary along insertion portion  820 . Namely, insertion portion  820  may have first width  850  at one end of insertion portion  820  and second width  852  at distal opening  852  that is the opposite end of insertion portion  820 . First width  850  may be greater than second width  852 . 
       FIG.  26    shows in particular how valve  807  may form a seal around tool  900  shaft  904 . In this embodiment, valve  807  may be a duckbill valve—and may be similar to duckbill valve  507  discussed above with respect to surgical cannula  500 . Specifically, valve  507  may include first lip  890  and second lip  892  that come together at seam  894 . In this way, the two lips  890 ,  892  may form a seal around tool  900  as shaft  904  extends through seam  894  and down through the remainder of cannula body  802  until portion  906  extends out distal opening  824 . 
       FIG.  27    is a perspective view of surgical cannula  800  with seal structure  804  removed from cannula body  802 . In this underside view of seal structure  804 , the structure of valve  807  may be seen in greater detail. That is, valve  807  includes first lip  890  and second lip  892  that meet at seam  894 . When no tool  900  is inserted into cannula  800 , valve  807  in its resting position, as shown in  FIG.  27   , forms a seal that prevents liquid or air to pass through when seal structure  804  is installed onto cannula  800 . 
       FIG.  28    is a top perspective view of surgical cannula  800  with seal structure  804  entirely removed from cannula body  802 . As discussed above with respect to other embodiments, seal structure  804  may include tether  814  and tether ring  818  that are configured to secure seal structure  804  to cannula body  802 . In this way, a medical practitioner may use tab portion  812  to reversibly remove seal structure  804  from cannula body  802  without losing track of seal structure  804 , as may be necessary during a surgical procedure. 
     Finally,  FIG.  29    is a cross-sectional perspective view of surgical cannula  800  with seal structure  804  removed from cannula body  802 . In this view, valve  807  is again clearly depicted as a duckbill valve having two lips  890 ,  892  that meet at seam  894 . This figure also shows how seal structure  804  may be reversibly attached to cannula body using retaining lip structures that may be substantially the same as discussed above with respect to surgical cannula  700 . 
     With respect to any embodiment discussed above, a cannula body portion in accordance with this disclosure may be substantially rigid. In some embodiments, the cannula body portion may be formed, at least in part, from a rigid material selected from the group consisting of polycarbonate and polypropylene. 
     While various embodiments are described, the description is intended to be exemplary, rather than limiting and it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible that are within the scope of the disclosed embodiments. Although many possible combinations of features are shown in the accompanying figures and discussed in this detailed description, many other combinations of the disclosed features are possible. Any feature or element of any embodiment may be used in combination with or substituted for any other feature or element in any other embodiment unless specifically restricted. Further, unless otherwise specified, any step in a method or function of a system may take place in any relative order in relation to any other step described herein.