Patent Publication Number: US-10779833-B2

Title: Anvil assembly delivery system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/564,571 filed Dec. 9, 2014, now U.S. Pat. No. 9,855,045, and the disclosure of the above-identified application is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     Technical Field 
     The present disclosure relates to an anvil assembly for use with a surgical stapling device. More particularly, the present disclosure relates to an anvil assembly for trans-oral delivery of the anvil assembly. 
     Background of Related Art 
     Trans-oral delivery systems for delivering an anvil assembly to a surgical site, e.g., the stomach, are known. In known delivery systems, a guide suture is threaded through one or more openings in the head of the anvil assembly to facilitate trans-oral insertion of the anvil assembly. The guide suture may be used to dislodge the anvil assembly if it becomes stuck within a body lumen during trans-oral delivery and/or to retrieve the anvil assembly in the event of an emergency, e.g., cardiac arrest. Improved methods for securing the guide suture to an anvil assembly to facilitate detachment of the guide suture from the anvil assembly once the anvil assembly is delivered to the surgical site and/or the stapling procedure has been performed is desirable. 
     SUMMARY 
     An anvil assembly for a surgical stapling device is provided. The anvil assembly includes an anvil center rod and a head assembly pivotally secured to the anvil center rod about a pivot axis. The head assembly is movable between an operative position and a tilted position. The head assembly includes a housing and cutting member supported within the housing. The housing includes an inner surface defining first and second openings for receiving a suture therethrough. The cutting member includes a knife engageable with the inner surface of the housing between the first and second openings to sever the suture. The inner surface may further include a recess formed between the first and second openings. In embodiments, the recess and the knife may be annular. The cutting member is movable from a first position spaced from the inner surface of the housing to a second position in contact with the inner surface of the housing. 
     In embodiments, the head assembly may further include a retainer member having an annular body portion and a frangible ring for maintaining the cutting member in the first position. Separation of the frangible ring from the annular body portion may permit movement of the cutting member from the first position to the second position. The anvil assembly may further include a biasing member positioned to urge the head assembly relative to the anvil center rod to position the head assembly in the tilted position. 
     Also provided is an anvil delivery system. The anvil delivery system includes an anvil assembly and a suture guide assembly. The suture guide assembly includes a guide suture secured to the head assembly and a reel assembly configured for selectively dispensing the guide suture. The guide suture may be received through the first opening in the housing and extend from the second opening in the housing. The reel assembly may include a reel housing and a reel member rotatably received within the reel housing. The guide suture may be supported about the reel member. The reel member may define an annular channel for receiving the guide suture. The reel member may be rotatably supported on the reel housing within an annular cavity in the housing. 
     In embodiments, the anvil delivery system further includes a tubular guide assembly for trans-oral insertion of the anvil assembly. The tubular guide assembly may include a flexible tube and an adapter configured for operably connecting the flexible tube to the anvil center rod. The tubular guide assembly may further include a retaining suture for retaining the head assembly of the anvil assembly in the tilted position. The retaining suture may be received through third and fourth openings in the housing and is secured between the adapter and the flexible tube. 
     In addition, a kit for performing a surgical stapling procedure is provided. The kit includes an anvil assembly, a suture guide, and a tubular guide assembly. The suture guide assembly may include a guide suture and a reel assembly. The tubular guide assembly may include a flexible tube and an adapter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments of the presently disclosed anvil assembly and anvil assembly delivery system are disclosed herein with reference to the drawings wherein: 
         FIG. 1  is a perspective view of a surgical stapling device including an embodiment of an anvil assembly according to the present disclosure; 
         FIG. 2  is a perspective side view of the anvil assembly of  FIG. 1  from the distal end; 
         FIG. 3  is a perspective side view of the anvil assembly shown in  FIGS. 1 and 2  from the proximal end; 
         FIG. 4  is an exploded side, perspective view of the anvil assembly of  FIGS. 1-3 ; 
         FIG. 5  is a distal end view of the anvil assembly of  FIGS. 1-4 ; 
         FIG. 6  is a side cross-sectional view taken along section line  6 - 6  of  FIG. 5 ; 
         FIG. 7  is a side cross-sectional view taken along section line  7 - 7  of  FIG. 5 ; 
         FIG. 8  is an enlarged side view of a cam latch member of the anvil assembly of  FIGS. 1-7 ; 
         FIG. 9  is a top view of the anvil assembly of  FIGS. 1-7  engaged with an anvil delivery system; 
         FIG. 10  is an enlarged exploded view of the anvil delivery system of  FIG. 9 ; 
         FIG. 11  an enlarged top view of the anvil delivery system of  FIGS. 9 and 10 , engaged with the anvil assembly of  FIGS. 1-7 ; 
         FIG. 12  is a side cross-sectional view taken along section line  12 - 12  of  FIG. 11 ; 
         FIG. 13  is a side cross sectional view of the anvil assembly of  FIGS. 1-7 , in a pre-fired tilted position, engaged with the anvil delivery system of  FIGS. 9-12 ; 
         FIG. 14  is an enlarged view of the indicated area of detail shown in  FIG. 13 ; 
         FIG. 15  is an illustration of the anvil assembly and anvil delivery system of  FIGS. 11 and 12  being inserted trans-orally into a patient; 
         FIG. 16  is an enlarged side view of the distal head portion of the surgical stapling device of  FIG. 1  with the anvil assembly removed; 
         FIG. 17  is an enlarged side view of the distal head portion of the surgical stapling device of  FIG. 1  with the anvil assembly of  FIGS. 1-7  received thereon; 
         FIG. 18  is an enlarged side cross-sectional view of the distal head portion of the surgical stapling device of  FIG. 1  and the anvil assembly of  FIGS. 1-7  in a pre-fired non-tilted operative position; 
         FIG. 19  is an enlarged side cross-sectional view of the distal head portion of the surgical stapling device of  FIG. 1  and the anvil assembly of  FIGS. 1-7  in a post-fired non-titled operative position; 
         FIG. 20  is an enlarged side cross-sectional view of the distal end of the anvil assembly of  FIGS. 1-7  in the post-fired operative position; 
         FIG. 21  is an enlarged side cross-sectional view of the distal end of the anvil assembly of  FIGS. 1-7  in a post-fired tilted position; 
         FIG. 22  is a side cross-sectional view of the anvil assembly of  FIGS. 1-7  in a post-fired tilted position supported on an anvil retainer of the surgical instrument of  FIG. 1 ; 
         FIG. 22A  is another side cross-sectional view of the anvil assembly of  FIGS. 1-7  in a post-fired tilted position supported on an anvil retainer of the surgical instrument of  FIG. 1   
         FIG. 23  is an enlarged view of the indicated area of detail shown in  FIG. 22A ; 
         FIG. 24  is a side view of the anvil assembly of  FIG. 22  supported on the anvil retainer of the surgical stapling device of  FIG. 1  in the post-fired tilted position; 
         FIG. 25  is a side perspective view of an anvil assembly according to another embodiment of the present disclosure in the operative position; 
         FIG. 26  is a side perspective view of the anvil assembly of  FIG. 25  in the first tilted position; 
         FIG. 27  is an exploded perspective view of the anvil assembly of  FIG. 25 ; 
         FIG. 28  is a bottom perspective view of a housing of the anvil assembly of  FIG. 25 ; 
         FIG. 28A  is an end view of the housing of the anvil assembly of  FIG. 25  from a proximal end; 
         FIG. 29  is a bottom perspective view of a head assembly of the anvil assembly of  FIG. 25 ; 
         FIG. 30  is a top perspective view of the anvil assembly of  FIG. 25  with the housing of  FIG. 28  removed; 
         FIG. 31  is a bottom perspective view of a backup member/cutting ring assembly of the anvil assembly of  FIG. 25 ; 
         FIG. 32  is a side cross-sectional view of the anvil assembly of  FIG. 25  in the operative position with the backup member/cutting ring assembly in a first or proximal position; and 
         FIG. 33  is a side cross-sectional view of the anvil assembly of  FIG. 25  in the operative position with the backup member/cutting ring assembly in a second or distal position. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Embodiments of the presently disclosed anvil assembly delivery system will now be described in detail with reference to the drawings in which like reference numerals designate identical or corresponding elements in each of the several views. Throughout this description, the term “proximal” will refer to the portion of the instrument closest to the operator and the term “distal” will refer to the portion of the instrument furthest from the operator. 
       FIG. 1  illustrates an embodiment of a surgical stapling device configured for use with tilt anvil assemblies according to the present disclosure. Briefly, surgical stapling device  10  includes a proximal handle assembly  12 , an elongated central body portion  14  including a curved elongated outer tube  14   a , and a distal head portion  16 . Alternately, in some surgical procedures, e.g., the treatment of hemorrhoids, it is desirable to have a substantially straight, shortened, central body portion. The length, shape and/or the diameter of body portion  14  and distal head portion  16  may also be varied to suit a particular surgical procedure. 
     With reference still to  FIG. 1 , handle assembly  12  includes a stationary handle  18 , a firing trigger  20 , a rotatable approximation knob  22  and an indicator  24 . A pivotally mounted trigger lock  26  is fastened to handle assembly  12  and is manually positioned to prevent inadvertent firing of stapling device  10 . Indicator  24  is positioned on the stationary handle  18  and includes indicia, e.g., color coding, alpha-numeric labeling, etc., to identify to a surgeon whether the device is approximated and is ready to be fired. Head portion  16  includes an anvil assembly  110  and a shell assembly  31 . For a more detailed discussion of surgical stapler  10 , please refer to commonly owned U.S. Pat. No. 7,364,060 to Milliman, the contents of which is incorporated herein by reference in its entirety. 
     Referring now to  FIGS. 2-7 , an anvil assembly according to an embodiment of the present disclosure is shown generally as anvil assembly  110 . Anvil assembly  110  is shown in a non-titled position or operative position. Anvil assembly  110  includes a head assembly  112  and a center rod assembly  114 . Head assembly  112  includes a post  116 , a housing  118 , a backup member or plate  120 , a cutting ring  122 , a cutting ring cover  123 , an anvil plate  124 , a spacer or washer  125 , a cam latch member  126 , and a retainer member  127 . Post  116  is monolithically formed with and centrally positioned within housing  118 . Alternately, housing  118  and post  116  may be formed separately and fastened together using a known fastening technique, e.g., welding. 
     As will be discussed in further detail below, housing  118  includes openings  119   a ,  119   b  sized and dimensioned to receive one or more sutures “S”. During use, a first suture “S 1 ” ( FIG. 9 ) is inserted through openings  119   a  and is used to retain head assembly  112  in a retracted or first tilted position ( FIG. 9 ) during insertion of anvil assembly  110  within a patient. A second suture “S 2 ” ( FIG. 9 ) is inserted through openings  119   b  and is configured to permit retrieval of tilt anvil assembly  110  from within a patient. During trans-oral insertion of anvil assembly  110 , suture “S 2 ” extends from the mouth of patient, permitting the anvil assembly  110  to be retrieved trans-orally. 
     With reference still to  FIGS. 2-7 , anvil plate  124  is supported in an outer annular recess  128  of housing  118  and includes a plurality of staple deforming pockets  130  for receiving and deforming staples. At least one tab  124   a  extends radially outwardly from anvil plate  124  and is received within a cutout  132  formed in an outer rim of housing  118 . Tab  124   a  and cutout  132  function to align or properly position anvil plate  124  within annular recess  128  of housing  118 . 
     With particular reference to  FIGS. 6 and 7 , head assembly  112  will be described in detail. Backup plate  120  includes a central opening  134  which is positioned about post  116  within an inner annular recess  136  of housing  118  between post  116  and outer annular recess  128 . Backup plate  120  includes a raised platform  120   a . Cutting ring  122  includes an opening  122   a  having a configuration substantially the same as platform  120   a . Although platform  120   a  is illustrated as having a circular shape, other configurations are envisioned, e.g., square, rectangular, triangular, etc. In one embodiment, cutting ring  122  is formed from polyethylene and is fixedly secured to backup plate  120  using, for example, an adhesive, to form a backup plate/cutting ring assembly. Backup plate  120  is formed from a hard material, e.g., a metal. Alternately other materials of construction may be used to construct backup plate  120  and cutting ring  122 . Further, backup plate  120  and cutting ring  122 , in the alternative, can be formed as a single or unitary structure. 
     Still referring to  FIGS. 6 and 7 , a cutting ring cover  123  is secured to an outwardly facing or proximal surface of cutting ring  122  using, for example, an adhesive. In one embodiment, cutting ring cover  123  is formed from a material or materials, which have a hardness greater than that of the cutting ring, e.g., mylar. In one embodiment, cutting ring cover  123  includes two layers of mylar (not shown) which are joined together using an adhesive and a polypropylene coating. Alternately, cutting ring  122  need not have a cover. Cutting ring  122  and backup plate  120  are slidably mounted about post  116 . Backup plate  120  includes a pair of inwardly extending fingers  138  which will be described in further detail below. 
     With reference still to  FIGS. 6 and 7 , retainer member  127  is positioned in inner annular recess  136  between backup plate  120  and a back wall  118   a  of housing  118 . In one embodiment, retainer member  127  is annular and includes a plurality of deformable tabs  127   a  which engage a rear surface of backup plate  120 . Retainer member  127  prevents backup plate  120  and cutting ring  122  from moving or being pushed into inner annular recess  136  of housing  118  until a predetermined force sufficient to deform tabs  127   a  has been applied to the backup plate/cutting ring assembly. The predetermined force can be close to but is less than the force applied by an annular cutting blade of a surgical stapling device when it engages, for example, the cutting ring of anvil assembly  110 . In one embodiment by way of example, the predetermined force is between about ten pounds and about ninety pounds and can be about thirty (30) pounds. When the predetermined force is reached, e.g., during cutting of tissue, backup plate  120  is urged into inner annular recess  136  and compresses retainer member  127 . It is envisioned that other crushable, deformable, collapsible or movement restricting members may be used to retain the backup plate/cutting ring assembly in a fixed position until a predetermined force has been applied to the backup plate/cutting ring assembly. 
     Turning back to  FIG. 4 , anvil center rod assembly  114  includes a center rod  152 , a plunger  154  and plunger spring  156 . A first end of center rod  152  includes a pair of arms  159  which define a cavity  159   a . Each arm  159  has a transverse throughbore  158  which is aligned with a central longitudinal axis of center rod  152 . Alternately, throughbores  158  can be offset from the longitudinal axis of center rod  152 . Post  116  of head assembly  112  is dimensioned to be positioned within cavity  159   a  and also includes a transverse throughbore (not shown). A pivot member  162  pivotally secures post  116  to center rod  152  via the through bores such that head assembly  112  may be pivotally mounted to anvil center rod assembly  114 . 
     Turning briefly to  FIG. 8 , cam latch member  126  includes a body  126   a  having a throughbore  126   b . Throughbore  126   b  is dimensioned to receive pivot member  162  such that cam latch member  126  is pivotally mounted within transverse slot  172  ( FIG. 3 ) of post  116  about pivot member  162 . Referring now to  FIGS. 3, 6 and 7 , cam latch member  126  includes a first body portion  126   c  which extends partially from slot  172  of post  116  and is positioned to be engaged by a finger  166  of plunger  154 . First body portion  126   c  is configured such that the distance between the surface of first body portion  126   c  and through bore  126   b  increase in a clockwise direction about cam latch member  126 . In this manner, plunger  154  is able to move forward as cam latch member  126  rotates in a clockwise direction. Additionally, this configuration of first body portion  126   c  permits plunger  154  to be retracted as cam latch member rotates in a counter-clockwise direction. Cam latch member  126  also includes an edge  126   f , including a tab  126   b . A leading portion of edge  126   f  is configured to be urged into engagement with an inner periphery  120   b  of backup plate  120  by an engagement finger  166  of plunger  154  when anvil head  112  is in its non-tilted or operative position. Tab  126   g  is configured to engage backwall  118   a  of housing  118  to prevent cam latch member  126  from rotating counter-clockwise relative to housing  118 . 
     With reference to  FIG. 6 , plunger  154  is slidably positioned in a bore  164  formed in the first end of center rod  152 . Plunger  154  includes an engagement finger  166  which is offset from the pivot axis of head assembly  112  and biased into engagement with an edge  126   c  of cam latch  126 . Engagement of finger  166  with edge  126   c  of cam latch  126  presses a leading portion of edge  126   f  against an inner periphery of back plate  120  to urge head assembly  112  to an operative or non-tilted position on center rod  152 . 
     Turning to  FIG. 7 , in the pre-fired operative position of head assembly  112 , i.e. when head assembly  112  has been pivoted to its non-tilted position, fingers  138  formed on backup plate  120  engage protrusions  152   b  adjacent top surface  152   a  of center rod  152  to prevent head assembly  112  from pivoting about pivot member  162 . Head assembly  112  may be tilted a degrees ( FIG. 13 ) relative to anvil center rod assembly  114  in the pre-fired tilted position. In one embodiment, head assembly  112  is tilted about seventy degrees (70°) in its pre-fired tilted position; however it should be understood that tilting head assembly  112  to other degrees is also contemplated. Titling of head assembly  112  relative to anvil center rod assembly  114  causes body portion  126   c  of cam latch member  126  to engage finger  166  of plunger  154 . As cam latch assembly  126  rotates with the tilting of head assembly  112 , plunger  154  is retracted with bore  164  of anvil center rod assembly  114 , thereby compressing spring  156 . In this manner, finger  166  of plunger  154  is distally biased against body portion  126   c  of cam latch member  126 . 
     With reference to  FIGS. 3 and 4 , a second end of center rod  152  includes a bore  180  defined by a plurality of flexible arms  182 . Flexible arms  182  each include an opening  182   a  dimensioned to receive a projection formed on or connected to a shell assembly  31  ( FIG. 18 ). Alternatively, openings  182   a  may be configured to receive a suture for permitting retrieval of anvil assembly  110 . The proximal ends of each of the flexible arms  182  include an internal shoulder  184  dimensioned to releasably engage shell assembly  31  of surgical stapling device  10  to secure anvil assembly  110  to the surgical stapling device. A plurality of splines  186  are formed about center rod  152 . Splines  186  function to align anvil assembly  110  with the staple holding portion of a surgical stapling device. Center rod  152  also includes an annular recessed portion  190  to facilitate grasping of anvil assembly  110  by a surgeon with a grasper. Recessed portion  190  may include a roughened or knurled surface or an overmold to facilitate grasping of anvil assembly  110 . 
     With reference now to  FIGS. 9-12 , a system for delivering anvil assembly  110  within a patient is shown generally as anvil delivery system  50 . Anvil delivery system  50  includes a flexible tube  52  and an adapter  62 . Flexible tube  52  includes an open end  52   a . Adapter  62  and anvil assembly  110  are supported on open end  52   a  of flexible tube  52 . Open end  52   a  of flexible tube  52  includes a through bore  53  extending therethrough configured to receive a locking pin  54 . Open end  52   a  further includes an opening  55 . Closed end  52   b  of flexible tube  52  is configured for trans-orally receipt in a patient. Flexible tube  52  may include markings or other gradations  56  along the length thereof to indicate to a surgeon how much of flexible tube  52  has been received within the patient during insertion and/or to indicate the length of flexible tube  52  remaining in the patient upon removal. 
     With particular reference to  FIG. 10 , adapter  62  includes a first end  62   a  configured to be received within open end  52   a  of flexible tube  52  and a second end  62   b  is configured to be received with in bore  180  formed in center rod  152  of anvil assembly  110 . First end  62   a  includes a series of annular rings  64  configured to frictionally retain first end  62   a  of adapter  62  within open end  52   a  of flexible tube  52 . Second end  62   b  of adapter  62  includes a longitudinal guide member  66  configured to be received between flexible arms  182  formed in center rod  152  of anvil assembly  110 . In addition, second end  62   b  of adapter  62  is sized to allow center rod  154  of anvil assembly  110  to freely slide into and off second end  62   b  of adapter  62 . Adapter  62  further includes a first through bore  70  formed in a central hub portion  62   c  as well as second and third through bores  72 ,  74  formed in first end  62   a . Through bore  72  is configured to align with through bore  53  formed in open end  52   a  of flexible tube  52  and is sized to receive locking pin  54 . 
     With particular reference now to  FIGS. 10, 13 and 14 , anvil assembly  110  is supported on anvil delivery system  50 . Securing anvil assembly  110  to anvil delivery system  50  requires first that suture “S 1 ” is thread through openings  119   a  formed on head assembly  112  such that first and second ends of suture “S 1 ” are positioned on opposites of center rod  152 . Next, second end  62   b  of adapter  62  is positioned within through bore  180  of center rod  152  such that longitudinal guide  66  is received between two of arm members  182 . Each of the first and second ends of suture “S 1 ” is inserted through opening  55  formed in open end  52   a  of flexible member  52 . Head assembly  112  is then rotated to a first tilted position while first and second ends of suture “S 1 ” are pulled through opening  55 . First end  62   a  of adapter  62  is then inserted into open end  52   a  of flexible member. The frictional contact between annular rings  64  of first end  62   a  of adapter  62  and an inner surface of flexible tube  52  secures adapter  62  to flexible tube  52  and prevents suture “S 1 ” from loosening. It is envisioned that more than one suture may be used to secure head assembly  112  in a pre-fired tilted position. 
     With reference now to  FIG. 15 , a method for delivering anvil assembly  110  to a surgical site within a patient will be described. In one method, anvil assembly  110  is provided in the first tilted position supported on anvil delivery system  50  and ready for delivery. Alternatively, a clinician secures anvil assembly  110  to anvil delivery system  50  as discussed above. Once anvil assembly  110  has been secured to flexible tube  52 , the surgeon inserts closed end  52   b  of flexible tube  52  in the patient&#39;s mouth “M” and moves closed end  52   b  along with flexible tube  52  down through esophagus “E” to a surgical site, i.e., the stomach “St”. 
     After insertion, the surgeon then makes a first incision “I 1 ” at the surgical site (stomach “St” as shown) to create an inner access to closed end  52   b  of flexible tube  52  and then pulls open end  52   b  of flexible tube  52  through first incision “I 1 ”. In some procedures it may be beneficial to pull flexible tube  52  through incision “I 1 ” until center rod  152  of anvil assembly  110  advances through first incision “I 1 ”. When anvil assembly  110  is properly positioned at the surgical site, the surgeon releases anvil delivery system  50  from anvil assembly  110  by cutting suture “S 1 ” and separating anvil assembly  110  from second end  62   b  of adapter  62 . Flexible tube  52  (with fitting  62 ) may then be pulled from the body through first incision “I 1 ”. 
     Severing of suture “S 1 ” permits plunger  154  to extend from within bore  164 , thereby causing finger  166  to engage body portion  126   c  of cam latch member  126 . Rotation of cam latch member  126  causes edge  126   f  of latch member  126  to move into engagement with the inner periphery of backup plate  120 , thereby urging head assembly  112  to return to a non-tilted operative position. Additionally, the distal end of stapling device  10  may be configured to engage finger  166  of plunger  154  as anvil assembly  110  is attached to surgical stapling device  10 . In this manner, the distal end of surgical stapling device  10  urges plunger  154  distally, thereby ensuring the rotation of head assembly  112  to a non-tilted position. 
     With particular reference to  FIG. 15 , in one method, a second incision “I 2 ” is then formed at the surgical site such that distal head portion  16  of surgical stapling device  10  may be received therethrough. Alternatively, distal head portion  16  of surgical stapling device  10  may be received through first incision “I 1 ” once anvil deliver system  50  has been removed therefrom. 
     Turning briefly to  FIGS. 16 and 17 , anvil assembly  110  is operably received on an anvil retainer  32  extending from shell assembly  31  formed on a distal end of surgical stapling device  10 . Once anvil assembly  110  is received on surgical stapling device  10 , surgical stapling device  10  operates in the manner discussed in the &#39;060 patent. 
     The operation of anvil assembly  110  will now be described with reference to  FIGS. 18-23 . When anvil assembly  110  is in its pre-fired non-tilted position, backup plate  120  is spaced from backwall  118   a  of housing  118  by retainer  127  and protrusions  152   b  of center rod  152  engage fingers  138  of backup plate  120  to prevent tilting of head assembly  112  about pivot member  162 . Finger  166  of plunger  154  is urged by spring  156  into engagement with body portion  126   c  of cam latch member  126  to urge cam latch member  126  in a clockwise direction, about pivot member  162  such that edge  126   f  of cam latch member  126  engages inner periphery  120   b  of backup member  120 . 
     The firing of surgical stapling device  10  causes a knife blade  33  thereof to engage cutting ring  122  to move cutting ring  122  and backup plate  120  into annular recess  136  of housing  118  of head assembly  112 . Arrows “W” in  FIG. 19  indicate how cutting ring  122  and backup plate  120  move as a result of the firing of surgical stapling device  10 . When such movement occurs, deformable tabs  127   a  of retainer  127  are deformed against backwall  118   a  of housing  118  and fingers  138  of backup member  120  move away from protrusions  152   b  of center rod  152 . Further, inner periphery  120   b  of backup plate  120  moves past edge  126   f  of cam latch member  126  such that cam latch member  126  is urged to pivot about pivot member  162  in the direction indicated by arrow “X” in  FIG. 21  by plunger  154  to a position in which body portion  126   d  is positioned in front of and engages backup plate  120 . Engagement of plunger  154  with cam latch member  126  urges head assembly  112  to a second tilted position ( FIGS. 22 and 23 ). It is noted that head assembly  112  will not immediately tilt upon firing of surgical stapling device  10  because, upon firing, head assembly  112  is in an approximated position, i.e., the head assembly  112  is in close alignment with shell assembly  31  of stapling device  10 , and, therefore, does not provide room for head assembly  112  to pivot. As such, the head assembly  112  will only begin to tilt when anvil assembly  110  and shell assembly  31  of surgical stapling device  10  are being unapproximated. 
     As head assembly  112  pivots towards its forward or second tilted position, finger  166  of plunger  154  maintains surface  126   e  of cam latch member  126  in contact with backup plate  120  to prevent backup plate  120  from sticking to the knife blade as the knife blade is retracted. It is noted that curved surface  126   e  of cam latch member is configured to eliminate any gap and ensure contact between surface  126   e  of cam latch member  126  and backup plate  120  to hold backup plate  120  in place during and after the knife blade is retracted such that the cutting ring and backup plate assembly stay in their correct position during continued tilting of anvil assembly  112 . Anvil assembly  110  is configured such that head assembly  112  tilts to a forward or second tilted position β degrees ( FIG. 23 ) relative to center rod assembly  114 . In one embodiment, head assembly  112  is tilted about seventy degrees (70°) to its second tilted position such that the total pivoting movement of the anvil from the retracted or first tilted position to the forward or second tilted position is about one-hundred and forty degrees (140°). It should, however, be noted that the tilting of head assembly  112  to other degrees is also contemplated. 
     As described above, the anvil assemblies of the present disclosure are configured to be delivered to a surgical site, e.g., the stomach “St” ( FIG. 15 ), trans-orally. During trans-oral delivery of the anvil assemblies, a retaining suture, i.e., first suture “S 1 ”, retains the head assembly of the anvil assembly in a first tilted position and a proximal guide suture, i.e., second suture “S 2 ”, includes first and second ends “S 2a ”, “S 2b ” that remain external of the patient&#39;s mouth “M” that allow the surgeon to dislodge or retrieve the anvil assembly from the patient during trans-oral delivery. 
     As described above and with reference to  FIG. 11 , second suture “S 2 ” is threaded through openings  119   b  in housing  118  of head assembly  112  of anvil assembly  110 . Detaching second suture “S 2 ” from anvil assembly  110  requires pulling on first end “S 2a ” of second suture “S 2 ” such that second end “S 2b ” of second suture “S 2 ” travels from external the patient&#39;s mouth “M” ( FIG. 15 ), where it is accessible by the surgeon, through the patient&#39;s mouth “M” and upper gastrointestinal (GI) tract, e.g., esophagus “E” and stomach “St” ( FIG. 15 ) and through the openings  119   b  in housing  118  of head assembly  112  of anvil assembly  110  before having to travel back through the upper GI tract and out the patient&#39;s mouth “M”. 
     With reference now to  FIGS. 25-33 , an anvil assembly according to alternate embodiment of the present disclosure is shown generally as anvil assembly  210 . As will be described in further detail below, anvil assembly  210  is configured such that second suture “S 2 ” ( FIG. 25 ) is severed during a stapling procedure to detach second suture “S 2 ” from anvil assembly  210  and to permit withdrawal of the second suture “S 2 ” from the patient by pulling on first and second ends “S 2a ”, “S 2b ” of the second suture “S 2 ”. In this manner, the second suture “S 2 ” is separated from the anvil assembly  210  and withdrawn from the patient without having to pull the second end “S 2b ” of the second suture “S 2 ” through the body lumen ( FIG. 15 ) of the patient, i.e., the mouth “M”, the esophagus “E”, and the stomach “St”. 
     With reference to  FIGS. 25-27 , the anvil assembly  210  is substantially similar to the anvil assembly  110  described hereinabove and will only be described in detail as relates to differences between the anvil assembly  210  and the anvil assembly  110 . The anvil assembly  210  includes a head assembly  212  and a center rod assembly  214 . The head assembly  212  is pivotable relative to the center rod assembly  214  and includes a housing  218 , a backup member  220 , a cutting ring  222 , and a retainer member  224 . An anvil plate  226  ( FIG. 28 ) is supported on an outer rim  230   b  ( FIG. 28 ) of the housing  218  and includes a plurality of staple deforming pockets  226   a  ( FIG. 28 ) for receiving and deforming staples (not shown). The center rod assembly  214  includes a center rod  252 , a plunger  254  for engaging the head assembly  212 , a plunger spring  256  for biasing the plunger  254  in a distal direction, a cam latch member  258  received within the head assembly  212 , and a pivot pin  260  pivotally connecting the head assembly  212  to the center rod  252 . 
     Referring to  FIGS. 27, 28, and 28A , the housing  218  of the head assembly  212  of the anvil assembly  210  includes a center post  230   a  and defines a cavity  231  between the center post  230   a  and the outer rim  230   b . An inner surface  218   a  of the housing  218  defines a recess  217  spaced outward from and formed about the center post  230   a  within the cavity  231 . A first and second pair of openings  219   a ,  219   b  ( FIG. 25 ) extend through the inner surface  218   a  of the housing  218 . The first pair of openings  219   a  receives the first suture “S 1 ” and the second pair of openings  219   b  receives the second suture “S 2 ”. More particularly, the second pair of openings  219   b  extends through the inner surface  218   a  of housing  218  on either side of the recess  217  such that when the second suture “S 2 ” ( FIG. 32 ) is received through the second pair of opening  219   b , the second suture “S 2 ” extends across the recess  217 . Although the recess  217  is shown as being annular and extending completely about the center post  230   a  of housing  218 , it is envisioned that recess  217  need only extend a distance to facilitate passage of the second suture “S 2 ” and, thus, may extend only partially about the center post  230   a . In alternative embodiments, housing  218  is formed without a recess  217  and the second suture “S 2 ” is received through the second pair of openings  219   b  and extends directly across the inner surface  218   a  of housing  218 . 
     With reference to  FIG. 27-31 , the backup member  220 , the cutting ring  222 , and the retainer member  224  are received within the cavity  231  ( FIG. 28A ) of the housing  218  about the center post  230   a  of housing  218 . The backup member  220  is secured to the cutting ring  222  to form a backup member/cutting ring assembly  225 . As shown, the backup member/cutting ring assembly  225  is formed by overmolding the backup member  220  to the cutting ring  222 . In particular, during the overmolding of the backup member  220  to the cutting ring  222 , a plurality of post  223  are formed that extend through openings  221  of the cutting ring  222  to secure the backup member  220  to the cutting ring  222 . Alternatively, the backup member/cutting ring assembly  225  is formed as a single component or as two components that are secured together using mechanical fasteners or in any other suitable manner. The backup member/cutting ring assembly  225  is movable within the cavity  231  from a proximal position ( FIG. 32 ) to a distal position ( FIG. 33 ). The backup member/cutting ring assembly  225  is retained in the proximal position ( FIG. 32 ) within the cavity  231  of the housing  218  by the retainer member  224 . 
     The retainer member  224  includes an annular body portion  224   a  and a frangible ring  224   b  supported on the annular body portion  224   a . The frangible ring  224   b  maintains the backup member/cutting ring assembly  225  in the proximal position until a predetermined force sufficient to fracture or separate the frangible ring  224   b  from the annular body portion  224   a  of the retainer member  224  is applied to the backup member/cutting ring assembly  225  by an annular knife  33  ( FIG. 19 ) of surgical stapling device  10  ( FIG. 1 ). The backup member/cutting ring assembly  225  is maintained within the cavity  231  of housing  218  by a plurality of tabs  222  ( FIG. 31 ) extending outwardly from cutting ring  222  and engaging the outer rim  230   b  of the housing  218 . 
     For a detailed description of the structure and function of an exemplary backup member/cutting ring assembly  225  and an exemplary retainer member  224 , please refer to commonly owned U.S. application Ser. No. 14/078,766, the content of which is incorporated herein by reference in its entirety. 
     The backup member/cutting ring assembly  225  includes a knife  232  that extends from a distal surface  220   a  of the backup member  220  and is aligned with the recess  217  defined within the housing  218 . When the backup member  220  is secured to cutting ring  222  to form the backup member/cutting ring assembly  225 , the knife  232  extends distally beyond the distal surface  220   a  ( FIG. 30 ) of the backup member  220  towards the recess  217 . Although shown has having an annular configuration and extending from the backup member  220 , it is envisioned that the knife  232  may include any configuration suitable for receipt within recess  217  formed in inner surface  218   a  ( FIG. 28 ) of housing  218 . For example, in embodiments, the length of the knife  232  corresponds to the length of the recess  217  and, thus, as discussed above with regard to recess  217 , need only be of a length to facilitate cutting of the second suture “S 2 ”. In embodiments of housing  218  without the recess  217 , knife  232  is configured to engage the inner surface  218   a  of housing  218 . 
     With particular reference now to  FIG. 32 , when the head assembly  212  of the anvil assembly  210  is in a pre-fired condition, the backup member/cutting ring assembly  225  and thus, the knife  232  extending from the backup member  220 , are longitudinally spaced from the inner surface  218   a  of the housing  218 . As noted above, the backup member/cutting ring assembly  225  is maintained in the proximal position through engagement with the frangible ring  224   b  of retainer member  224  and is retained within the cavity  231  of the housing  218  through engagement of the plurality of tabs  222   a  of the cutting ring  222  with the outer rim  230   b  of the housing  218 . 
     As discussed above with respect to  FIG. 19 , during firing of the surgical stapling device  10 , an annular knife  33  is advanced distally from shell assembly  31 , as indicated by arrow “w”. With reference now to  FIG. 32 , when the anvil assembly  210  is attached to the shell assembly  31  ( FIG. 19 ) of surgical stapling device  10  ( FIG. 19 ), distal movement of the annular knife  33  ( FIG. 19 ) causes the knife  33  to engage the cutting ring  222  of the backup member/cutting ring assembly  225  of the head assembly  212 . When the predetermined force required to separate or fracture the frangible ring  224   b  of the retainer member  224  from the annular body portion  224   a  of the retainer member  224  is applied to the frangible ring  224   b  by the knife  33 , the backup member/cutting ring assembly  225  is moved distally within the cavity  231  of the housing  218  about the center post  230   a . Continued force from the knife  33  causes the backup member/cutting ring assembly  225  to move distally until the backup member/cutting ring assembly  225  engages the inner surface  218   a  of the housing  218 . As the backup member/cutting ring assembly  225  is moved distally, the knife  232  of the backup member  220  is received within the recess  217  formed in the inner surface  218   a  of the housing  218  causing the knife  232  to engage and sever second suture “S 2 ”. 
     Once the second suture “S 2 ” is severed, each half of the severed second suture “S 2 ” is independently removed trans-orally from the patient by pulling on the first and second ends “S 2a ”, “S 2b ” of the second suture “S 2 ”. By severing the second suture “S 2 ” in this manner, the surgeon is able to disengage the second suture “S 2 ” from the anvil assembly  210  and directly remove each half of the second suture “S 2 ” from within the patient without having to pull the second end “S 2b ” of second suture “S 2 ” through the openings  219   b  in the anvil assembly  210  and back out of a patient through the body lumen. If the second suture “S 2 ” were to be removed from the patient without severing the suture into two halves, one end “S 2a ”, “S 2b ” of the second suture “S 2 ” would have to be pulled into the body lumen of the patient and through the anvil assembly  210  before being pulled back through the body lumen. 
     As noted above, the second suture “S 2 ” facilitates placement of the anvil assembly  210  within the stomach “St” ( FIG. 15 ) of the patient. The second suture “S 2 ” may be used to dislodge the anvil assembly  210  if it becomes stuck within a body lumen during trans-oral delivery and/or to retrieve the anvil assembly  210  in the event of an emergency. Since the second suture “S 2 ” remains attached to the anvil assembly  210  throughout the placement and attachment of the anvil assembly  210  to the surgical stapling device  10  ( FIG. 1 ), and until the stapling procedure is completed, the second suture “S 2 ” may be used to dislodge and/or retrieve the anvil assembly  210  at any point up to the second suture “S 2 ” being severed. 
     Persons skilled in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments. It is envisioned that the elements and features illustrated or described in connection with one exemplary embodiment may be combined with the elements and features of another without departing from the scope of the present disclosure. As well, one skilled in the art will appreciate further features and advantages of the disclosure based on the above-described embodiments. Accordingly, the disclosure is not to be limited by what has been particularly shown and described, except as indicated by the appended claims.