Abstract:
A surgical stapling apparatus including a handle assembly, an elongated shaft extending distally from the handle assembly, a shell assembly containing a plurality of staples arranged in an annular array, and a firing mechanism for advancing staples from the shell assembly. An anvil assembly including a tiltable anvil head movable from an aligned operative position to a tilted position. A camera assembly is operatively coupled to a distal surface of the tiltable anvil head such that an orientation of the camera assembly changes as the anvil head moves from the operative to the tilted position.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of and priority to U.S. Provisional Patent Application No. 61/638,533, filed Apr. 26, 2012, the entire disclosure of which is incorporated by reference herein. 
     
    
     BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present disclosure relates generally to a surgical instrument including a camera. More particularly, the present disclosure relates to a surgical circular stapling device for applying surgical staples to body tissue which device includes a camera. 
         [0004]    2. Background of Related Art 
         [0005]    Anastomosis is the surgical joining of separate hollow organ sections. Typically, an anastomosis procedure follows surgery in which a diseased or defective section of hollow tissue is removed and the remaining end sections are to be joined. Depending on the desired anastomosis procedure, the end sections may be joined by either circular, end-to-end or side-to-side organ reconstruction methods. 
         [0006]    In a circular anastomosis procedure, the two ends of the organ sections are joined by means of a stapling instrument, which drives a circular array of staples through the end section of each organ section and simultaneously cores any tissue interior of the driven circular array of staples to free the tubular passage. Examples of instruments for performing circular anastomosis of hollow organs are described in U.S. Pat. Nos. 7,303,106, 6,053,390, 5,588,579, 5,119,983, 5,005,749, 4,646,745, 4,576,167, and 4,473,077, each of which is incorporated herein in its entirety by reference. Typically, these instruments include an elongated shaft having a handle portion, at a proximal end, to actuate the instrument and a staple holding component disposed at a distal end. An anvil assembly including an anvil rod with attached anvil head is mounted to the distal end of the instrument adjacent the staple holding component. Opposed end portions of tissue of the hollow organ(s) to be stapled are clamped between the anvil head and the staple holding component. The clamped tissue is stapled by driving one or more staples from the staple holding component so that the ends of the staples pass through the tissue and are deformed by the anvil head. An annular knife is concurrently advanced to core tissue with the hollow organ to free a tubular passage within the organ. 
         [0007]    Besides anastomosis of hollow organs, surgical stapling devices for performing circular anastomosis have been used to treat internal hemorrhoids in the rectum. Typically, during use of a circular stapling device for hemorrhoid treatment, the anvil head and the staple holding component of the surgical stapling device are inserted through the anus and into the rectum with the anvil head and the staple holding component in an open or unapproximated position. Thereafter, a pursestring suture is used to pull the internal hemorrhoidal tissue towards the anvil rod. Next, the anvil head and the staple holding component are approximated to clamp the hemorrhoid tissue between the anvil head and the staple holding component. The stapling device is fired to remove the hemorrhoidal tissue and staple the cut tissue. 
         [0008]    It would be advantageous to increase visibility of the tissue during certain surgical procedures using the circular stapling device. Additionally, in certain instances, it would be advantageous to view the staple line after application of the surgical staplers. Currently, visual aids, such as endoscopes, may be inserted into the surgical site to view the anastomosis. This however requires removal of the stapler and time consuming insertion of the endoscope. 
       SUMMARY 
       [0009]    In accordance with the present disclosure, a circular surgical stapling device for performing circular anastomosis and/or treating internal hemorrhoids is disclosed. The surgical stapling device includes a handle portion or assembly, a body portion and a head portion including an anvil assembly and a shell assembly. The handle portion can include a rotatable approximation knob for approximating the anvil and shell assemblies and a firing trigger for actuating a firing mechanism for ejecting staples positioned within the shell assembly. 
         [0010]    The anvil assembly includes a tiltable anvil that provides a reduced anvil profile to reduce trauma during removal. The tiltable anvil tilts automatically when the device has been fired and unapproximated. A camera assembly is operatively coupled to a surface of the tiltable anvil. The camera assembly includes a lens that is positioned on a surface of the tiltable anvil such that when the tiltable anvil is in the tilted position, the lens is directed towards the staple line, thereby facilitating viewing of the staple line prior to removal of the surgical stapling device from the surgical site. 
         [0011]    The camera assembly may be configured and adapted to wirelessly transmit images taken by the lens. Moreover, the camera assembly may be configured and adapted to wirelessly and/or remotely receive instruction. In addition, the camera assembly may include an internal power source. The camera assembly may also include a light source to illuminate the surgical site to facilitate capturing of images. Moreover, the camera assembly may be shaped to approximate and conform to the surface of the tiltable anvil and may also include an adhesive backing to facilitate affixing the camera assembly to the surface of the tiltable anvil. Without the camera assembly operatively coupled to the surgical stapling device, as described herein, a surgeon would otherwise have to remove the stapling device and insert another instrument, i.e., an endoscope, into the surgical site to view the staple line to ensure proper joining of the organ sections. 
         [0012]    These and other embodiments of the present disclosure will be described in greater detail below with reference to the appended figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    Various embodiment of the presently disclosed surgical stapling device are disclosed herein with reference to the drawings, wherein: 
           [0014]      FIG. 1  is a top side perspective view from the proximal end of the presently disclosed surgical stapling device in the unapproximated position; 
           [0015]      FIG. 2  is a top side perspective view from the distal end of the surgical stapling device shown in  FIG. 1 ; 
           [0016]      FIG. 3  is a side perspective exploded view of the handle assembly of the surgical stapling device shown in  FIG. 1 ; 
           [0017]      FIG. 3A  is a top perspective view of the indicator of the handle assembly shown in  FIG. 3 ; 
           [0018]      FIG. 4  is a side perspective view from the top of the handle assembly of the surgical stapling device shown in  FIG. 1  with a handle section removed; 
           [0019]      FIG. 5  is a side perspective view from the bottom of the handle assembly of the surgical stapling device shown in  FIG. 4 ; 
           [0020]      FIG. 6  is a side perspective exploded view of the central body portion and distal head portion of the surgical stapling device shown in  FIG. 1 ; 
           [0021]      FIG. 7  is an enlarged side perspective of the anvil retainer and band portions of the central body portion shown in  FIG. 6 ; 
           [0022]      FIG. 8  is a side perspective view of the screw and screw stop of the approximation mechanism of the handle assembly shown in  FIG. 5 ; 
           [0023]      FIG. 9  is an enlarged view of the indicated area of detail shown in  FIG. 3 ; 
           [0024]      FIG. 9A  is a side perspective view from the top of the abutment member of the handle assembly shown in  FIG. 3 ; 
           [0025]      FIG. 10  is a side perspective exploded view from the proximal end of the anvil assembly of the surgical stapling device shown in  FIG. 1 ; 
           [0026]      FIG. 11  is a side perspective view of the retaining clip of the anvil assembly shown in  FIG. 10 ; 
           [0027]      FIG. 12  is a side perspective view of the distal end of the center rod of the anvil assembly shown in  FIG. 10  with a removable trocar fastened thereto; 
           [0028]      FIG. 13  is a side perspective view of the center rod and removable trocar shown in  FIG. 11  separated one from the other; 
           [0029]      FIG. 14  is a side perspective view from the proximal end of the anvil assembly shown in  FIG. 10  with the removable trocar attached thereto; 
           [0030]      FIG. 15  is a side perspective view from the distal end of the anvil assembly shown in  FIG. 14 ; 
           [0031]      FIG. 16  is a side cross-sectional view taken through the retaining clip of the anvil assembly and removable trocar of the anvil assembly shown in  FIG. 15 ; 
           [0032]      FIG. 17  is an enlarged view of the indicated area of detail shown in  FIG. 16 ; 
           [0033]      FIG. 18  is a side cross-sectional view taken through the pivot member of the anvil head assembly of the anvil assembly shown in  FIG. 15 ; 
           [0034]      FIG. 19  is a side perspective view from the proximal end of the anvil assembly shown in  FIG. 18  with the removable trocar removed; 
           [0035]      FIG. 20  is a perspective, partial cutaway view from the distal end of the anvil assembly shown in  FIG. 19 , with the anvil head removed; 
           [0036]      FIG. 21  is a side cross-sectional partial cutaway view of the distal portion of the anvil assembly shown in  FIG. 19 , with the anvil head in phantom; 
           [0037]      FIG. 22  is a side perspective view from the bottom of the screw stop of the handle assembly shown in  FIG. 3 ; 
           [0038]      FIG. 23  is a bottom perspective view from the proximal end of the screw stop shown in  FIG. 22 ; 
           [0039]      FIG. 24  is a top perspective view of the cam adjustment member of the handle assembly shown in  FIG. 3 ; 
           [0040]      FIG. 25  is a side view of the screw and screw stop of the handle assembly shown in  FIG. 3  with the set screw and the cam adjustment member removed; 
           [0041]      FIG. 26  is a side view of the screw and screw stop shown in  FIG. 25  with the set screw and cam adjustment member attached thereto; 
           [0042]      FIG. 27  is a side view of the screw and screw stop shown in  FIG. 26  with the cam adjustment screw adjusted to increase the tissue gap; 
           [0043]      FIG. 28  is a side view of the screw and screw stop shown in  FIG. 26  with the cam adjustment screw adjusted to decrease the tissue gap; 
           [0044]      FIG. 29  is a top perspective view from the proximal end of the slide member of the indicator mechanism of the handle assembly shown in  FIG. 3 ; 
           [0045]      FIG. 30  is a bottom perspective view of the lockout member of the fire lockout mechanism of the handle assembly shown in  FIG. 3 ; 
           [0046]      FIG. 31  is a side cross-sectional view of the surgical stapling device shown in  FIG. 1  with the anvil assembly removed; 
           [0047]      FIG. 32  is a side enlarged view of the handle assembly of the surgical stapling device shown in  FIG. 31  with the handle sections removed; 
           [0048]      FIG. 33  is an enlarged view of the indicated area of detail shown in  FIG. 31 ; 
           [0049]      FIG. 34  is an enlarged view of the indicated area of detail shown in  FIG. 31 ; 
           [0050]      FIG. 35  is a perspective view from the front of the distal end of the surgical stapling device shown in  FIG. 31  with the anvil assembly removed; 
           [0051]      FIG. 36  is a perspective view from the front of the distal end of the surgical stapling device shown in  FIG. 35  with an anvil assembly attached thereto; 
           [0052]      FIG. 37  is a side cross-sectional view of the distal end of the surgical stapling device shown in  FIG. 36 ; 
           [0053]      FIG. 38  is a side cross-sectional view of the surgical stapling device shown in  FIG. 31  with the anvil assembly attached thereto; 
           [0054]      FIG. 39  is a cross-sectional view taken along section lines  39 - 39  of  FIG. 38 ; 
           [0055]      FIG. 40  is a cross-sectional view taken along section lines  40 - 40  of  FIG. 38 ; 
           [0056]      FIG. 41  is a cross-sectional view taken along section lines  41 - 41  of  FIG. 38 ; 
           [0057]      FIG. 42  is a cross-sectional view taken along section lines  42 - 42  of  FIG. 38 ; 
           [0058]      FIG. 43  is a cross-sectional view taken along section lines  43 - 43  of  FIG. 38 ; 
           [0059]      FIG. 44  is a cross-sectional view taken along section lines  44 - 44  of  FIG. 38 ; 
           [0060]      FIG. 45  is a side perspective view of the surgical stapling device shown in  FIG. 38  with the anvil assembly in an approximated position; 
           [0061]      FIG. 46  is a side cross-sectional view of the distal end of the surgical stapling device shown in  FIG. 45 ; 
           [0062]      FIG. 47  is a side enlarged view of the handle assembly of the surgical stapling device shown in  FIG. 45  with a handle section removed; 
           [0063]      FIG. 48  is a side cross-sectional view of the handle assembly of the surgical stapling device shown in  FIG. 45 ; 
           [0064]      FIG. 49  is a top horizontal cross-sectional view of a portion of the handle assembly of the surgical stapling device shown in  FIG. 45 ; 
           [0065]      FIG. 50  is a side view of a portion of the handle assembly of the surgical stapler shown in  FIG. 45  with the handle sections removed; 
           [0066]      FIG. 51  is a side cross-sectional view of a portion of the handle assembly of the surgical stapling device shown in  FIG. 45  after the firing trigger has been actuated; 
           [0067]      FIG. 52  is a side cross-sectional view of the distal end of the surgical stapling device shown in  FIG. 45  after the firing trigger has been actuated; 
           [0068]      FIG. 53  is a side view of the handle assembly shown in  FIG. 51  with the handle sections removed; 
           [0069]      FIG. 54  is an enlarged view of the firing link extension engaging the abutment member of the tactile indicator mechanism of the handle assembly shown in  FIG. 53 ; 
           [0070]      FIG. 55  is a side cross-sectional view of the distal portion of the anvil assembly of the surgical stapling device shown in  FIG. 52 ; 
           [0071]      FIG. 56  is a side cross-sectional view of the distal portion of the anvil assembly shown in  FIG. 55  with a portion of the anvil head assembly in phantom; 
           [0072]      FIG. 57  is a side view of the surgical stapling device shown in  FIG. 45  after the anvil assembly and cartridge assembly have been unapproximated a distance sufficient to permit the anvil head assembly to pivot on the anvil center rod; 
           [0073]      FIG. 58  is an enlarged view of the abutment member of the tactile indicator mechanism of the handle assembly shown in  FIG. 53  (during unapproximation of the anvil and cartridge assemblies) with the wing of the screw stop, shown in phantom, in engagement with the abutment member; 
           [0074]      FIG. 59  is a side cross-sectional view of the anvil assembly shown in  FIG. 56  as the anvil head assembly begins to tilt; 
           [0075]      FIG. 60  is a side cross-sectional view of the anvil assembly shown in  FIG. 59  with the anvil assembly tilted; 
           [0076]      FIG. 61  is a side view of the surgical stapling device shown in  FIG. 45  with the anvil head assembly unapproximated and tilted; 
           [0077]      FIG. 62  is a side cross-sectional view of another embodiment of the presently disclosed surgical stapling device with the anvil assembly removed from the anvil retainer; 
           [0078]      FIG. 63  is a side cross-sectional view of the surgical stapling device shown in  FIG. 62  with the anvil assembly attached to the anvil retainer in the open position; 
           [0079]      FIG. 64  is a side cross-sectional view of the anvil assembly of the surgical stapling device shown in  FIG. 63 ; 
           [0080]      FIG. 65  is a side cross-sectional view of the surgical stapling device shown in  FIG. 63  with the anvil assembly in the approximated position; 
           [0081]      FIG. 66  is a side perspective view from the proximal end of the retainer extension of the surgical stapling device shown in  FIG. 65 ; 
           [0082]      FIG. 67  is a side view of the retainer extension shown in  FIG. 66 ; 
           [0083]      FIG. 68  is a top cross-sectional view of the retainer extension shown in  FIG. 67 ; 
           [0084]      FIG. 69  is a top view of the anvil retainer of the surgical stapling device shown in  FIG. 65 ; 
           [0085]      FIG. 70  is a side view of the anvil retainer shown in  FIG. 69 ; 
           [0086]      FIG. 71  is an enlarged view of the indicated area of detail shown in  FIG. 70 ; 
           [0087]      FIG. 72  is a side view of the outer housing portion of the shell assembly of the surgical stapling device shown in  FIG. 65 ; 
           [0088]      FIG. 73  is a top view of the outer housing portion of the shell assembly shown in  FIG. 72 ; 
           [0089]      FIG. 74  is a cross-sectional view taken along section lines  74 - 74  of  FIG. 72 ; 
           [0090]      FIG. 75  is a cross-sectional view taken along section lines  75 - 75  of  FIG. 73 ; 
           [0091]      FIG. 76  is a side view of the inner guide portion of the shell assembly of the surgical stapling device shown in  FIG. 65 ; 
           [0092]      FIG. 77  is a top view of the inner guide portion of the shell assembly shown in  FIG. 76 ; 
           [0093]      FIG. 78  is a side cross-sectional view of the inner guide portion of the shell assembly shown in  FIG. 77 ; 
           [0094]      FIG. 79  is a top cross-sectional view of the inner guide portion of the shell assembly shown in  FIG. 77 ; 
           [0095]      FIG. 80  is a side view of the pusher of the surgical stapling device shown in  FIG. 65 ; 
           [0096]      FIG. 81  is a top view of the pusher shown in  FIG. 80 ; 
           [0097]      FIG. 82  is a side cross-sectional view of the pusher shown in  FIG. 81 ; 
           [0098]      FIG. 83  is a top cross-sectional view of the pusher shown in  FIG. 82 ; 
           [0099]      FIG. 84  is a side cross-sectional view of the anvil assembly of the surgical stapling device shown in  FIG. 65 ; 
           [0100]      FIG. 85  is a top cross-sectional view of the anvil assembly of the surgical stapling device shown in  FIG. 84 ; 
           [0101]      FIG. 86  is a top view of the anvil center rod of the anvil assembly shown in  FIG. 85 ; 
           [0102]      FIG. 87  is a side view of the anvil center rod of the anvil assembly shown in  FIG. 85 ; 
           [0103]      FIG. 88  is a side cross-sectional view of the anvil head of the anvil assembly shown in  FIG. 85 ; 
           [0104]      FIG. 89  is a side view of the anvil head shown in  FIG. 88 ; 
           [0105]      FIG. 90  is a side cross-sectional view of the anvil center rod shown in  FIG. 87 ; 
           [0106]      FIG. 91  is a side view of the anvil cover of the anvil assembly shown in  FIG. 84 ; 
           [0107]      FIG. 92  is a side cross-sectional view of the anvil cover shown in  FIG. 91 ; 
           [0108]      FIG. 93  is a side cross-sectional view of an anvil assembly insertion handle; 
           [0109]      FIG. 94  is a side perspective view of the anvil assembly insertion handle shown in  FIG. 93 ; 
           [0110]      FIG. 95  is a side cross-sectional view of the anvil assembly insertion handle attached to the anvil assembly shown in  FIG. 84 ; 
           [0111]      FIG. 96  is a top view of a speculum suitable for use with the presently disclosed surgical stapling device; 
           [0112]      FIG. 97  is a side perspective view from above of the speculum shown in  FIG. 96 ; 
           [0113]      FIG. 99  is a side cross-sectional view of the speculum shown in  FIG. 97 ; 
           [0114]      FIG. 100  is a top side perspective view of a surgical stapling device as shown in  FIG. 1 , in which the surgical stapling device includes an anvil including a camera assembly coupled thereto; 
           [0115]      FIG. 101  is a side view of the surgical stapling device of  FIG. 100  after the anvil and cartridge assembly have been unapproximated (after firing of the staples) a distance sufficient to permit the anvil head assembly to pivot on the anvil center rod; 
           [0116]      FIG. 102  is a side perspective view from the distal end of the anvil assembly of the surgical stapling device shown in  FIG. 100 ; 
           [0117]      FIG. 103  is a side cross-sectional view taken through the anvil assembly of  FIG. 102 ; 
           [0118]      FIG. 104  is an enlarged view of the indicated area of detail shown in  FIG. 103 ; 
           [0119]      FIG. 105  is a side cross-sectional view of the distal portion of the anvil assembly of the surgical stapling device shown in  FIG. 102 ; 
           [0120]      FIG. 106  is a side cross-sectional view of the distal portion of the anvil assembly shown in  FIG. 105  with a portion of the anvil head assembly in phantom; 
           [0121]      FIG. 107  is a side cross-sectional view of the anvil assembly shown in  FIG. 106  as the anvil head assembly begins to tilt; 
           [0122]      FIG. 108  is a side cross-sectional view of the anvil assembly shown in  FIG. 107  with the anvil head assembly tilted; and 
           [0123]      FIG. 109  is a side view of the camera assembly of  FIG. 100  shown with a removable liner partially removed. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0124]    Embodiments of the presently disclosed surgical stapling device 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. 
         [0125]      FIGS. 1 and 2  illustrate one embodiment of the presently disclosed surgical stapling device shown generally as  10 . 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 central body portion. The length, shape and/or the diameter of body portion  14  and head portion  16  may also be varied to suit a particular surgical procedure. 
         [0126]    Handle assembly  12  includes a stationary handle  18 , a firing trigger  20 , a rotatable approximation knob  22  and an indicator  24 . Stationary handle  18  may be formed from thermoplastic handle sections  18   a  and  18   b,  e.g., polycarbonate, ( FIG. 3 ) which together define a housing for the internal components of handle assembly  12 . Handle sections  18   a  and  18   b  may be secured together by sonic welding. Alternately, other known securement techniques may be employed including screws, adhesives, snap-fit connectors, etc. The internal components of handle portion  12  will be discussed in detail below. In one embodiment, cushioned and/or resilient slip resistant portions such as a grip (not shown) can be fastened to or included as part of handle sections  18   a  and  18   b  and firing trigger  20 . The slip resistant grip may be formed over handle sections  18   a  and  18   b  and firing trigger  20  using an overmolding procedure and may be formed from Neoprene polychloroprene or rubber. Alternately, other suitable, e.g., elastomeric, materials and joining techniques may be employed. 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 has been fired and/or when the device is ready to be fired. 
         [0127]    Head portion  16  includes an anvil assembly  30  and a shell assembly  31 . Each of these assemblies will be discussed in detail below. Except where otherwise noted, the components of surgical device  10  are formed from thermoplastics including polycarbonates, and metals including stainless steel and aluminum. The particular material selected to form a particular component will depend upon the strength requirements of the particular component. For example, the anvil may be formed from a metal, such as stainless steel, and the stationary handle may be formed from a thermoplastic such as polycarbonate. Alternately, other materials not listed above, which can withstand sterilization procedures, may be used to form components of stapling device  10  provided the materials are suitable for surgical use and meet the strength requirements of the particular component. 
         [0128]      FIGS. 3-5  illustrate the internal components of handle assembly  12 . The internal components include the proximal components of approximation and firing mechanisms, a firing lockout mechanism and an indicator drive mechanism.  FIGS. 6 and 7  illustrate the internal components of elongated body portion  14 . These components include the distal components of the approximation and firing mechanisms. Each of these mechanisms will be disclosed in detail hereinbelow. 
       Approximation Mechanism 
       [0129]    Referring to  FIGS. 3-8 , the approximation mechanism includes approximation knob  22 , a rotatable sleeve  33 , a drive screw  32 , first and second screw extensions  34  and  36  ( FIG. 6 ), and an anvil retainer  38 . Rotatable sleeve  33  includes a substantially cylindrical hollow body portion  40  and a substantially cylindrical collar  42  which together define a central bore  33   a.  Collar  42  has an annular groove  44  formed thereabout and is dimensioned to receive an inwardly extending flange  46  formed on an inner wall of stationary handle  18 . Engagement between groove  44  and flange  46  axially fixes sleeve  33  within handle  18  while permitting rotation of sleeve  33  in relation to stationary handle  18 . The proximal end of body portion  40  of rotatable sleeve  33  extends through an opening  18   b  in the proximal end of stationary handle  18 . A pair of diametrically opposed elongated ribs  48  are positioned on the outer surface of body portion  40 . Approximation knob  22  includes a pair of internal slots  49   a  positioned to receive ribs  48  of sleeve  33  to rotatably fix sleeve  33  to knob  22 , such that rotation of knob  22  causes concurrent rotation of sleeve  33 . 
         [0130]    The proximal half of screw  32  includes a helical channel  50  and is dimensioned to be slidably positioned within central bore  33   a  of rotatable sleeve  33 . The distal end of screw  32  includes an annular recess  35  dimensioned to receive a seal member  37  ( FIG. 3 ) for providing a fluid tight seal between the outer surface of screw  32  and the inner surface of pusher link  74  ( FIG. 6 ). A pin  52  ( FIG. 3 ) extends radially through body portion  42  of sleeve  33  into helical channel  50 . Since sleeve  33  is axially fixed with respect to stationary handle  18 , rotation of sleeve  33  about screw  32  causes pin  52  to move along channel  50  of screw  32  to effect axial movement of screw  32  within stationary handle  18 . 
         [0131]    The distal end of screw  32  includes a transverse slot  54 . Top and bottom screw extensions  34  and  36  ( FIG. 6 ) each include a proximally located flexible flat band portion  58  and a distally located flat band portion  60 . Alternately, it is envisioned that screw extensions  34  and  36  may have other than a band configuration. For example, screw extensions  34  and  36  may be semi-circular or circular in cross-section. The flexibility of top and bottom screw extensions  34  and  36  permits movement of screw extensions  34  and  36  through curved elongated body portion  14 . The proximal end of each band portion  58  includes a hole  62  dimensioned to receive a pin  64  for securing the proximal end of screw extensions  34  and  36  within transverse slot  54  of screw  32 . Alternately, other fastening techniques may be used to secure each band portion  58  to screw  32 , e.g., welding, crimping, etc. Distally located band portion  60  of each screw extension  34  and  36  is dimensioned to be received within a transverse slot  66  formed in a proximal end of anvil retainer  38  ( FIG. 7 ) to fasten anvil retainer  38  to the distal end of screw extensions  34  and  36 . In one embodiment, a pair of pins  66   a  which extend through the proximal end of anvil retainer  38  and band portions  60  are used to secure screw extensions  34  and  36  to anvil retainer  38 . Alternately, band portions  60  can be brazed or welded within slot  66  or other fastening techniques may be used to secure band portions  60  of screw extensions  34  and  36  to anvil retainer  38 , e.g., screws, crimping, etc. Anvil retainer  38  includes an annular protrusion  177  ( FIG. 7 ) which is configured to engage the anvil assembly in a manner to be discussed in detail below. Alternately, protrusion  177  need not be annular or may include different attachment structure, e.g., recesses, grooves, etc. 
         [0132]    In operation, when approximation knob  22  is manually rotated, rotatable sleeve  33  is rotated about the proximal end of screw  32  to move pin  52  along helical channel  50  of screw  32 . Since sleeve  33  is axially fixed to stationary handle  18 , as pin  52  is moved through channel  50 , screw  32  is advanced or retracted within stationary handle  18 . As a result, top and bottom screw extensions  34  and  36 , which are fastened to the distal end of screw  32 , and anvil retainer  38 , which is fastened to the distal end of screw extensions  34  and  36 , are moved axially within elongated body portion  14 . Since anvil assembly  30  is secured to the distal end of anvil retainer  38 , rotation of approximation knob  22  will effect movement of anvil assembly  30  in relation to shell assembly  31  between spaced and approximated positions. 
       Firing Mechanism 
       [0133]    Referring to  FIGS. 3-6  and  9 , the firing mechanism includes firing trigger  20 , a firing link  72  and an elongated pusher link  74  ( FIG. 6 ). Firing trigger  20  includes a body portion  76  and a trigger cover  80 . A cushioned gripping surface (not shown) which may be formed of Neoprene polychloroprene or rubber is provided on trigger cover  80 . The cushioned gripping surface provides a non-slip cushioned surface to make actuation of device  10  more comfortable and less traumatic to a surgeon. Body portion  76  of trigger  20  is pivotally connected to a coupling member  86  (which is secured to the proximal end of pusher link  74 ), by a pivot member  84 . Coupling member  86  may be formed integrally with pusher link  74  or as a separate element fastened thereto. Firing link  72  has a first end pivotally secured to body portion  76  of trigger  20  by a pivot member  87  and a second end pivotally secured within a vertical slot  82  formed between stationary handle half-sections  18   a  and  18   b  of stationary handle  18  by pivot member  79 . Pivot member  79  is free to move vertically within slot  82 . A spring  82   a  ( FIG. 9 ) is supported within handle  18  to urge pivot member  79  downwardly towards the bottom of slot  82 . Body portion  76  further includes a pair of abutments including an abutment  89  and an abutment  91  which are positioned to engage the distal end  26   a  ( FIG. 4 ) of trigger lock  26  in a manner to be described in greater detail below to prevent actuation of trigger  20  prior to approximation of device  10 . 
         [0134]    Coupling member  86  which is supported on the proximal end of elongated pusher link  74  includes a flange  104  ( FIG. 6 ). A spring  106 , positioned between an inner wall or abutment within stationary handle  18  and flange  104 , biases pusher link  74  proximally to a retracted, non-fired position. A pair of wings  108  extend radially outwardly from coupling member  86 . Wings  108  are dimensioned to slide along channel  111  ( FIG. 3 ) formed along the internal walls of stationary handle  18  to maintain proper alignment of pusher link  74  within stationary handle  18  during firing of device  10 . 
         [0135]    The distal end of pusher link  74  includes a pair of engagement fingers  110  which are dimensioned to lockingly engage with members  220  formed in the proximal end of pusher back  186 . Pusher back  186  forms part of shell assembly  31  and will be discussed in greater detail below. Pusher link  74  may be formed from a flexible plastic material and includes a plurality of notches  187  which allow the pusher link to bend more easily as it moves through body  14 . Pusher link  74  defines a hollow channel  75  for slidably receiving the approximation mechanism. A flat surface or cutout  74   a  formed in pusher link  74  slidably supports screw extensions  34  and  36  which are positioned in juxtaposed alignment one on top of the other. Spacers  77  are positioned within outer tube  14   a  adjacent cutout  74   a  to provide additional support for screw extensions  34  and  36  and pusher link  74  and prevent each component from buckling during actuation. An annular channel  74   b  is formed about pusher link  74  to receive an O-ring seal  74   c.  Pusher link  74  is slidably positioned within body portion  14  such that O-ring  74   c  seals the space between pusher link  74  and an internal wall of outer tube  14   a.  Operation of the firing mechanism of the device will be described in detail below. 
         [0136]    When firing trigger  20  is actuated, i.e., pivoted about pivot member  84 , firing link  72  is moved proximally until pivot member  79  engages an abutment surface  307  ( FIGS. 25 ,  28  and  48 ) formed on screw stop  306 . Screw stop  306  is axially fixed to screw  32 . When firing trigger  20  is pushed distally, pusher link  74  is advanced distally against the bias of spring  106 . Turning again to  FIG. 6 , since the distal end of pusher link  74  is connected to pusher back  186 , actuation of firing trigger  20  effects advancement of pusher back  186  within shell assembly  31  to eject staples from shell assembly  31  in a manner to be described below. 
       Anvil Assembly 
       [0137]    Referring to  FIGS. 10-21 , anvil assembly  30  includes an anvil head assembly  120  and an anvil center rod assembly  152 . Anvil head assembly  120  includes a post  122 , an anvil head  124 , a backup plate  126 , a cutting ring  128 , an anvil  129  and a retaining clip  127 . Post  122  is centrally positioned through a bore in anvil head  124 . Anvil  129  is supported on anvil head  124  in an outer annular recess  136  and includes a plurality of pockets  140  for receiving and deforming staples. At least one tab  129   a  extends radially outwardly from anvil  129  and is dimensioned to be received within a cutout  124   a  formed in anvil head  124 . Tab  129   a  and cutout  124   a  function to align anvil  129  within annular recess  136 . Backup plate  126  includes a central opening  126   b  which is positioned about post  122  within an inner recess  134  of anvil head  124  between post  122  and annular recess  136 . Backup ring  126  includes a raised platform  126   a.  Cutting ring  128  includes an opening  128   a  having a configuration substantially the same as platform  126   a.  Opening  128   a  is positioned about platform  126   a  to rotatably fix cutting ring  128   a  on backup ring  126 . In one embodiment, cutting ring  128  is formed from polyethylene and is fixedly secured to backup plate  126  using, for example, an adhesive. Backup ring  126  may be formed from a harder material such as a metal. Alternately other materials of construction may be used to construct plate  126  and ring  128 . Cutting ring  128  and backup plate  126  are slidably mounted about post  122 . Backup plate  126  includes a pair of inwardly extending tabs  150  which will be described in further detail below. Cutting ring  128  includes tabs  128   b,  which are received within cutouts  124   b  formed in anvil head  124  to properly align backup ring  126  and cutting ring  128  within anvil head  124 . 
         [0138]    Anvil center rod assembly  152  includes anvil center rod  154 , a plunger  156  and plunger spring  158 . A first end of center rod  154  includes a transverse throughbore  160  which is offset from the central longitudinal axis of center rod  154 . Post  122  of anvil head assembly  120  also includes a transverse throughbore  162 . A pivot member  164  pivotably secures post  122  to center rod  154  such that anvil head assembly  120  is pivotably mounted to anvil center rod assembly  152 . Plunger  156  is slidably positioned in a bore  154   b  ( FIG. 16 ) formed in the first end of center rod  154 . Plunger  156  includes an engagement finger  168  which is offset from the pivot axis of anvil head assembly  120  and biased into engagement with the base  122   a  of post  122  by plunger spring  158  to urge anvil head assembly  120  to a pivoted position orthogonal to center rod  154 . In a prefired position, tabs  150  formed on backup plate  126  engage a top surface  154   a  ( FIG. 20 ) of center rod  154  to prevent anvil head assembly  120  from pivoting about pivot member  164 . As device  10  is fired, backup plate  126  and cutting ring  128  are moved deeper into anvil recess  134  of anvil head  124  about post  122  ( FIG. 21 ) by knife  188  ( FIG. 6 ) in a manner to be described in further detail below. Movement of backup plate  126  and cutting ring  128  into anvil recess  134  moves tabs  150  out of engagement with top surface  154   a  of center rod  154  to permit plunger  156  to pivot anvil head assembly  120  about pivot member  164 . 
         [0139]    A retainer clip  127  is positioned in a transverse slot  122   c  formed in post  122  and includes a pair of outwardly biased flexible arms  127   a  and  127   b.  Arm  127   b  includes a recess  127   c  dimensioned to receive pivot pin  164  ( FIG. 17 ). Prior to firing device  10 , arms  127   a  and  127   b  are deformed inwardly by backup plate  126  ( FIG. 17 ). After device  10  has been fired and backup plate  126  has been pushed deeper into anvil head  124  by knife  188 , flexible arms  127   a  and  127   b  spring outwardly to a position in front of backup plate  126 . In this position, arms  127   a  and  127   b  prevent cutting ring  128  and backup plate  126  from sticking to knife  188  when anvil assembly  30  is unapproximated. 
         [0140]    A second end of center rod  154  includes a bore  170  defined by a plurality of flexible arms  155 . Bore  170  is dimensioned to receive a removable trocar  157  ( FIG. 12 ). Flexible arms  155  each include an opening  155   a  dimensioned to receive a projection  157   d  formed on removable trocar  157  to releasably secure trocar  157  to center rod  154  ( FIG. 13 ). The distal ends of each of flexible arms  155  include an internal shoulder  155   b  dimensioned to releasably engage anvil retainer  38  ( FIG. 6 ) in a manner to be discussed in detail below. A plurality of splines  181  ( FIG. 10 ) are formed about center rod  154  and are dimensioned to be received within grooves  196   a  ( FIG. 6 ) in shell assembly  31  to align anvil assembly  30  with shell assembly  31  during approximation of the anvil and shell assemblies. Center rod  154  also includes an annular recessed portion  183  to facilitate grasping of anvil assembly  30  by a surgeon with a grasper. 
         [0141]    Turning again to  FIG. 12-15 , Removable trocar  157  includes a trocar tip  157   a,  a body portion  157   b  and a cantilevered arm  157   c.  Projection  157   d  is positioned on the end of cantilevered arm  157   c.  Arm  157   c  is deflectable downwardly, i.e., radially inwardly, in the direction indicated by arrow “A” in  FIG. 13  to facilitate insertion of body portion  157   b  into bore  170  of center rod  154 . Splines  157   e  are provided on body portion  157   b  to properly align trocar  157  within bore  170  of center rod  154 . Arm  157   c  biases projection  157   d  outwardly such that when projection  157   d  passes beneath opening  155   a  in center rod  154 , projection  157   d  snaps into opening  155   a  to releasably secure removable trocar  157  to center rod  154 . A tab  157   f  is positioned on arm  157   c  and can be depressed to facilitate removal of trocar  157  from center rod  154 . Trocar tip  157   a  includes a throughbore  157   g  dimensioned to receive a suture (not shown) to facilitate locating and removal of trocar  157  within and from the human body. Although illustrated as having a sharpened tip, other trocar tip configurations are envisioned, e.g., blunt. 
       Shell Assembly 
       [0142]    Referring to  FIG. 6 , shell assembly  31  includes a shell  182 , a pusher back  186 , a cylindrical knife  188 , and a staple guide  192 . Shell  182  includes an outer housing portion  194  and an inner guide portion  196  having grooves  196   a  for mating with splines  181  on anvil center rod  154  ( FIG. 10 ). Outer housing portion  194  defines a throughbore  198  having a distal cylindrical section  200 , a central conical section  202  and a proximal smaller diameter cylindrical section  204 . A plurality of openings  206  may be formed in conical section  202 . Openings  206  are dimensioned to permit fluid and tissue passage during operation of the device. A pair of diametrically opposed flexible engagement members  207  are formed on proximal cylindrical section  204  of shell  182 . Engagement members  207  are positioned to be received in openings  207   a  formed on the distal end of outer tube  14   a  to secure shell  182  to elongated body  14 . A pair of openings  211  formed in the proximal end of outer tube  14   a  are dimensioned to receive protrusions (not shown) formed on the internal wall of stationary handle  18  ( FIG. 1 ) to facilitate attachment of tube  14   a  to handle portion  12 . 
         [0143]    Turning again to  FIG. 6  Pusher back  186  includes a central throughbore  208  which is slidably positioned about inner guide portion  196  of shell  182 . Pusher back  186  includes a distal cylindrical section  210  which is slidably positioned within distal cylindrical section  200  of shell  182 , a central conical section  212  and a proximal smaller diameter cylindrical section  214 . The proximal end of pusher back  186  includes members  220  which are configured to lockingly engage with resilient fingers  110  of pusher link  74  to fasten pusher link  74  to pusher back  186  such that a distal face of pusher link  74  abuts a proximal face of pusher back  186 . 
         [0144]    The distal end of pusher back  186  includes a pusher  190 . Pusher  190  includes a multiplicity of distally extending fingers  226  dimensioned to be slidably received within slots  228  formed in staple guide  192  to eject staples  230  therefrom. Cylindrical knife  188  is frictionally retained within the central throughbore of pusher back  186  to fixedly secure knife  188  in relation to pusher  190 . Alternately, knife  188  may be retained within pusher back  186  using adhesives, crimping, pins, etc. The distal end of knife  188  includes a circular cutting edge  234 . 
         [0145]    In operation, when pusher link  74  is advanced distally in response to actuation of firing trigger  20 , as will be described below, pusher back  186  is advanced distally within shell  182 . Advancement of pusher back  186  advances fingers  226  through slots  228  of staple guide  192  to advance staples  230  positioned within slots  228  and eject staples  230  from staple guide  192  into staple deforming pockets  140  of anvil  129  ( FIG. 11 ). Since knife  188  is secured to pusher back  186 , knife  188  is also advanced distally to core tissue as will be described in more detail below. 
         [0146]    A rigid bushing  209  is supported in the proximal end of inner guide portion  196  of shell  182 . Bushing  209  defines a throughbore dimensioned to slidably receive anvil retainer  38  and center rod  154  ( FIG. 10 ) of anvil assembly  30 . Bushing  209  provides lateral support for flexible arms  155  of center rod  154  when the anvil assembly  30  has been approximated to prevent disengagement of anvil assembly  30  from anvil retainer  38 . In the unapproximated position, flexible arms  155  of center rod  154  are positioned externally of bushing  209  to permit removal of anvil assembly  30  from retainer  38 . 
       Cam Adjustment Mechanism 
       [0147]    Referring to FIGS.  8  and  22 - 28 , a cam adjustment member  400  is secured by set screw  312  onto a sidewall  306   a  of screw stop  306  within a recess  306   b  formed in sidewall  306   a.  Cam adjustment member  400  includes a circular disc  402  having a throughbore  404 . Throughbore  404  is eccentrically formed through disc  402  and is dimensioned to receive set screw  312 . A smaller notch or hole  406  is also formed in disc  402  and is dimensioned to receive the tip of an adjustment tool (not shown). Recess  306   b  ( FIG. 22 ) includes a forward abutment shoulder or surface  306   c  ( FIG. 23 ) and a rear abutment surface  306   d  and is dimensioned to receive disc  402  such that the outer edge of disc  402  abuts forward and rear abutment surfaces  306   c  and  306   d.    
         [0148]    Set screw  312  extends through disc  402  and screw stop  306  and is received in a threaded bore  32   a  in screw  32  to secure screw stop  306  in position on screw  32 . Cam adjustment member  400  functions to adjust the axial position of screw stop  306  on screw  32 . More specifically, set screw  312  can be loosened to allow disc  402  to rotate within recess  306   b  of screw stop  306  while still remaining fixed to screw  32 . Since disc  402  is eccentrically mounted about screw  32  and engages forward and rear abutment surfaces  306   c  and  306   d  of recess  306   b,  rotation of disc  402  about fixed set screw  312  will urge screw stop  306  axially along screw  32  to adjust the axial position of screw stop  306  on screw  32 . For example, when disc  402  is rotated in a clockwise direction (as viewed in  FIG. 28 ) identified by arrow “B”, screw stop  306  will be moved axially in relation to screw  32  in the direction indicated by arrow “C” in response to engagement between the outer edge of disc  402  and rear shoulder  306   d  of recess  306   b.  Conversely, when disc  402  is rotated in a counter-clockwise direction (as viewed in  FIG. 27 ), identified by arrow “D”, screw stop  306  will be moved axially in relation to screw  32  in the direction indicated by arrow “E” in response to engagement between the outer edge of disc  402  and forward shoulder  306   c  of recess  306   b.    
         [0149]    When stapling device  10  is in a fully approximated position (as can be seen for instance in  FIG. 65 ), i.e., anvil assembly  30 ,  640  and shell assembly  31 ,  605  are brought into juxtaposed alignment to define a tissue receiving clearance, screw stop  306  ( FIG. 47 ) abuts against body portion  42  of the rotatable sleeve  33 , i.e., sleeve  33  functions as a stop for the approximation mechanism. In this position, anvil assembly  30  and shell assembly  31  are spaced slightly to define a tissue receiving clearance. By providing cam adjustment member  400 , the tissue receiving clearance can be selectively adjusted to be within a desired range by adjusting the position of screw stop  306  on screw  32 . In one embodiment, cam adjustment member  400  permits adjustment of the tissue receiving clearance of ±0.045 inches, although greater or lesser adjustment capabilities are also envisioned. Typically, adjustments to the tissue receiving clearance will be made by the device manufacturer. Alternately, a hole or opening (not shown) may be provided in handle portion  12  ( FIG. 1 ) to provide direct access to adjustment member  400  to allow for adjustment of the tissue receiving clearance at the surgical site. 
       Indicator Mechanism 
       [0150]    Referring to  FIGS. 3-5 ,  9 ,  22 ,  29  and  33 , the indicator mechanism includes indicator  24 , lens cover  24   a  and slide member  500 . Indicator  24  is pivotally supported about a pivot member  502  which may be formed monolithically with handle sections  18   a  and  18   b.  Lens cover  24   a  is positioned above indicator  24  and may be formed of magnification material to facilitate easy visualization of indicator  24 . Slide member  500  ( FIG. 29 ) includes a body portion  504  having an elongated slot  506  formed therein, a distal abutment member or upturned lip portion  508 , and a proximal extension  510 . Slide member  500  is slidably positioned between handle sections  18   a  and  18   b.  Proximal extension  510  is slidably supported within stationary handle  18  by support structure  516  ( FIG. 5 ). A biasing member  512 , e.g., a coil spring, is positioned in compression about proximal extension  510  between support structure  516  and body portion  504  of slide member  500  to urge slide member  500  distally within stationary handle  18 . Indicator  24  includes a pair of downwardly extending projections  518  and  520  positioned about pivot member  502 . Upturned lip portion  508  of slide member  500  is positioned between projections  518  and  520  and is positioned to engage projections  518  and  520  as it moves within stationary handle  18 . In the unfired position of device  10 , biasing member  512  urges slide member  500  distally to move lip portion  508  into engagement with projection  518  to pivot indicator to a first position, which provides indication to a surgeon that the device has not been approximated and is not in a fire-ready condition. 
         [0151]    As discussed above, screw stop  306  is fixedly attached to screw  32 . Screw stop  306  includes a first engagement member  522  which is positioned to travel through slot  506  and engage the proximal end  506   a  of slot  506  during approximation of the device. When engagement member  522  abuts proximal end  506   a  ( FIG. 29 ) of slot  506 , further approximation of device  10  moves slide plate  500  proximally within stationary handle  18  against the bias of spring  512  such that upturned lip  508  of slide member  500  engages projections  518  &amp;  520  of indicator  24 . (See  FIG. 48 ). Engagement between projections  518  &amp;  520  and lip  508  causes indicator  24  to pivot about pivot member  502  to a second position. In the second position, indicator  24  provides indication to a surgeon that the device has been approximated and is now in a fire-ready position. 
       Fire-Lockout Mechanism 
       [0152]    Referring to  FIGS. 3-5 ,  22 ,  30 ,  33 , and  47 , the firing-lockout mechanism includes trigger lock  26  and lockout member  530 . Trigger lock  26  is pivotally supported within bores  532  in handle sections  18   a  and  18   b  about pivot member  534 . In one embodiment, pivot member  534  extends from an upper edge of trigger lock  26  and is T-shaped and frictionally engages the inner wall of bores  532  to prevent free rotation of trigger lock  26 . Tip  26   a  ( FIG. 5 ) of trigger lock  26  is positioned between abutments  89  and  91  on body portion  76  of firing trigger  20  to prevent actuation of trigger  20  when trigger lock  26  is in the locked position. Trigger lock  26  also includes a proximal extension  26   b  ( FIG. 4 ) which will be discussed in further detail below. 
         [0153]    Lockout member  530  ( FIG. 30 ) includes a body portion  536 , a proximal extension  538 , a pair of front legs  540   a,  a pair of rear legs  540   b,  and an abutment member or downturned lip portion  542 . Lockout member  530  is slidably positioned between first and second stops  544  and  546  ( FIG. 5 ) formed on an internal wall of handle sections  18   a  and  18   b.  Stop  544  is positioned to engage rear legs  540   b  and stop  546  is positioned to engage front legs  540   a.  It is also envisioned that a single abutment member may be substituted for each pair of legs. A biasing member  548 , e.g., a coil spring, is positioned between stop  544  and body  536  about proximal extension  538  to urge lockout  530  to its distal-most position with legs  540   a  abutting stop  546 . In this position, extension  26   b  of trigger lock  26  is positioned beneath lip portion  542  of lockout member  530  to prevent pivotal movement of trigger lock  26 , and thus prevent actuation of stapling device  10 . 
         [0154]    As discussed above and as shown in  FIG. 47 , screw stop  306  is secured to screw  32 . A second engagement member or members  548  extend downwardly from screw stop  306 . (See  FIG. 22 ). When stapling device  10  is approximated and screw  32  is moved proximally within stationary handle  18 , engagement member  548  abuts front legs  540   a  of lockout member  530  to move lockout member  530  proximally against the bias of member  548  to a position in which lip portion  542  is spaced proximally of extension  26   b  of trigger lock  26 . In this position of lockout member  530 , trigger lock  526  can be pivoted to permit firing of stapling device  10 . 
       Tactile Indicator Mechanism 
       [0155]    Referring to  FIGS. 3 ,  5 ,  9  and  9 A, a tactile indicator mechanism provided in stationary handle  18  includes an abutment member  580  which is slidably positioned in a vertical slot  582  defined within handle sections  18   a  and  18   b.  Abutment member  580  includes a protuberance  580   a  and a guide rib  580   b.  Protuberance  580   a  is dimensioned to be received within one of two detents  582   a  and  582   b  formed along a wall of slot  582 . Abutment member  580  is movable from a retracted (downward) position, wherein protuberance  580   a  is positioned within detent  582   a,  to an extended (upward) position, wherein protuberance  580   a  is positioned within detent  582   b.  Engagement between protuberance  580   a  and detents  582   a  and  582   b  retains abutment member  580  in the respective position. Detent  582   c,  formed in vertical slot  582 , is sized to slidably receive guide rib  580   b  and thereby maintain member  580  in contact with slot  582 . 
         [0156]    Prior to firing of stapling device  10 , abutment member  580  is located in the retracted (downward) position ( FIG. 5 ). When device  10  is fired, an extension  590  of firing link  72  engages abutment member  580  and moves abutment member  580  from its retracted to its extended position. In the extended position, abutment member  580  extends into channel  111  of stationary handle  18 . 
         [0157]    Screw stop  306  includes a pair of wings  584  which are slidably positioned in channel  111  of stationary handle  18 . After stapling device  10  has been fired, abutment member  580  is positioned within channel  111 . During unapproximation of anvil assembly  150  and cartridge assembly  31 , one of the wings  584  of screw stop  306  engage abutment member  580  when the device has been unapproximated a sufficient distance to allow anvil assembly  30  to pivot to its reduced profile position (as will be discussed in mere detail below and as can be seen in  FIG. 57 ). Engagement between abutment member  580  and wing  584  of screw stop  306  provides a tactile and/or an audible indication to the surgeon that the anvil assembly  120  has tilted and stapling device  10  can be removed from a patient. If the surgical stapling device is unapproximated further, wing  584  will force abutment member  580  from the extended position back to the retracted position. 
       Operation 
       [0158]    Operation of surgical stapling device  10  will now be described in detail with reference to 
         [0159]      FIGS. 31-61 . 
         [0160]      FIGS. 31-35  illustrate surgical stapling device  10  in the unapproximated or open position prior to attachment of anvil assembly  30  to anvil retainer  38 . In this position, biasing member  106  is engaged with coupling  86  to urge pusher link  74  to its proximal-most position in which coupling  86  abuts screw-stop  306 . Biasing member  512  is engaged with slide member  500  of the indicator mechanism to position slide member  500  in engagement with projection  518  of indicator  24  to pivot indicator  24  in a clockwise direction, as viewed in  FIG. 33 . Biasing member  549  is engaged with body  536  of lockout member  530  to urge lockout member  530  to its distal-most position, wherein lip portion  542  of lockout member  530  is positioned above extension  26   b  of trigger lock  26  to prevent movement of trigger lock  26  to the unlocked position. Biasing member  82   a  engages pivot member  79  to urge pivot member  79  to the base of vertical slot  82 . Tactile indicator  580  is in the retracted or downward position with protrusion  580   a  positioned with detent  582   a.    
         [0161]      FIGS. 36-44  illustrate surgical stapling device  10  with anvil assembly  30  attached to anvil retainer  38  and the anvil assembly  30  in the unapproximated or open position. Referring to  FIGS. 37 and 38 , during attachment of anvil assembly  30  to anvil retainer  38 , anvil retainer  38  is positioned within bore  170  of center rod  154  of anvil assembly  30 . Flexible arms  155  deflect outwardly to accommodate center rod  154 . Center rod  154  is advanced onto anvil retainer  38  in the direction indicated by arrow “K” in  FIG. 37  until internal shoulder  155   b  of flexible arms  155  passes over annular protrusion  177  formed on anvil retainer  38 . At this point, resilient legs  155  releasably engage the anvil retainer. The position of the remaining components of stapling device are unaffected by attachment of anvil assembly  30  to anvil retainer  38  and remain as described above and shown in  FIGS. 31-35 . 
         [0162]      FIGS. 45-50  illustrate surgical stapling device  10  during movement of anvil assembly  30  and cartridge assembly  31  to the approximated or closed position. As discussed above, anvil assembly  30  is moved to the approximated or closed position by rotating rotation knob  22  in the direction indicated by arrow “L” in  FIG. 45 . Rotation of knob  22  causes cylindrical sleeve  33  to rotate to move pin  52  along helical channel  50  of screw  32 . Movement of pin  52  ( FIG. 48 ) along helical channel  50  causes screw  32  to translate within sleeve  33 . The distal end of screw  32  is connected to screw extensions  34  and  36  which are fastened at their distal ends to anvil retainer  38 . As such, retraction of screw  32  within sleeve  33  is translated into proximal movement of anvil retainer  38  and anvil assembly  30 . It is noted that when anvil assembly  30  is approximated, flexible legs  155  of center rod  154  are drawn into bushing  209  to lock legs  155  onto anvil retainer  38 . (See  FIG. 46 ). 
         [0163]    As discussed above, screw stop  306  ( FIG. 47 ) is axially fixed to screw  32  by set screw  312 . Thus, as screw  32  is retracted within sleeve  33 , screw stop  306  is moved from a distal position within stationary handle  18  to a proximal position. As screw stop  306  moves from the distal position to the proximal position, first engagement member  522  formed on screw stop  306  abuts proximal end  506   a  of slot  506  of slide plate  500  and moves slide plate  500  proximally against the bias of spring  512 . As slide plate  500  moves proximally, lip  508  of slide member  500  engages projections  518  &amp;  520  of indicator  24  to pivot indicator  24  in a counter-clockwise direction as viewed in  FIG. 48 . 
         [0164]    Screw stop  306  also includes a second engagement member  548  ( FIG. 47 ). As screw stop  306  is moved from the distal position to the proximal position during approximation of anvil assembly  30 , second engagement member  548  engages distal legs  540   a  of lockout member  530  to move lockout member  530  proximally to a position in which lip portion  542  is spaced proximally of extension  26   b  of trigger lock  26 . In this position, trigger lock  26  can be pivoted to an unlocked position to permit firing of stapling device  10 . 
         [0165]    Movement of screw stop  306  to its proximal-most position within stationary handle  18  positions abutment surface  307  ( FIG. 48 ) of screw stop  306  in position to engage pivot member  79  of firing link  72 . Abutment surface  307  comprises a substantially concave surface which is positioned to partially capture and act as a backstop for pivot  79  during firing of the stapling device. 
         [0166]      FIGS. 51-56  illustrate surgical stapling device  10  during the firing stroke of firing trigger  20 . As trigger  20  is compressed towards stationary handle  18  (as shown by the arrow in  FIG. 51 ), pivot member  79  engages abutment surface  307  on screw stop  306  and firing trigger  20  is pushed distally. As discussed above, the distal end of firing trigger  22  is connected through coupling member  86  to the proximal end of pusher link  74 . Accordingly, as firing trigger  20  is moved distally, pusher link  74  is moved distally to effect advancement of pusher back  186  within shell assembly  31 . Fingers  190  of pusher back  186  engage and eject staples  230  from staple guide  192  ( FIG. 52 ). 
         [0167]    Cylindrical knife  188  is moved concurrently with pusher back  186  such that knife  188  moves into engagement with cutting ring  128  and backup plate  126 . As discussed above, cutting ring  128  may be formed from polyethylene and backup plate  126  may be formed from a metal. When knife  188  engages cutting ring  128 , it cuts into cutting ring  128  and pushes backup plate  126  deeper into anvil head  124  to move tabs  150  from engagement with top surface  154   a  of center rod  154  ( FIG. 56 ). Anvil head  124  is now free to pivot about member  164  and is urged to do so by plunger  156 . It is noted that because the anvil assembly is in juxtaposed alignment with shell assembly  31 , the anvil head  14  will not pivot fully until the anvil and shell assemblies have been unapproximated a distance sufficient to allow the anvil head to fully pivot. When backup plate  126  moves into anvil head  124 , flexible arms  127   a  and  127   b  of retainer clip  127  spring outwardly to a position in front of backup plate  126  blocking movement of backup plate  126  out of anvil head  124  ( FIG. 55 ). As discussed above, arms  127   a  and  127   b  prevent backup plate  126  from sticking to knife  188  when anvil assembly  30  is returned to the unapproximated position. 
         [0168]    Referring to  FIGS. 57-60 , during unapproximation of stapling device  10  after device  10  has been fired, wing  584  of screw stop  306  engages tactile indicator  580  ( FIG. 58 ) at the point of unapproximation at which anvil assembly  124  is able to pivot to its tilted reduced profile position. Contact between wing  584  and tactile indicator  580  provides a tactile and/or audible indication that anvil head  124  has tilted. If additional force is provided to approximation knob  22 , wing  584  of screw stop  306  will force tactile indicator to the retracted position to allow stapling device  10  to move to the fully open position. In this position, flexible arms  155  are positioned distally of bushing  209  and anvil assembly  30  can be disengaged from anvil retainer  28 . 
         [0169]      FIGS. 62-91  illustrate another embodiment of the presently disclosed surgical stapling device shown generally as  600 . Stapling device  600  is configured and dimensioned to be particularly suitable for use in surgical procedures for removing internal hemorrhoids from a patient. Briefly, surgical stapling device  600  includes a proximal handle assembly  601 , a central body portion  603  and a distal head portion  605 . The handle assembly  601  is substantially identical to handle assembly  12  of surgical stapling device  10  and will not be discussed in further detail herein. 
         [0170]    Referring to  FIGS. 62-71 , the approximation mechanism of surgical stapling device  600  includes an approximation knob  602 , a rotatable sleeve  604 , a drive screw  606 , a retainer extension  608 , and an anvil retainer  610 . Approximation knob  602 , rotatable sleeve  604  and drive screw  606  are substantially identical to the like named components described above with respect to surgical stapling device  10  and will not be described in further detail herein. Referring to  FIGS. 66-68 , retainer extension  608  includes a proximal end  612  defining a bore  614  dimensioned to receive the distal end of drive screw  606 . A pair of transverse openings  618  extend through sidewalls of the proximal end of retainer extension  608  to facilitate attachment of retainer extension  608  to the distal end of drive screw  606  with a pin or screw  620  ( FIG. 62 ). Alternately, other known attachment devices may be used, e.g., welding, brazing, screw threads, etc. The distal end of retainer extension  608  includes a flat finger  622  configured to be received within a slot  624  ( FIG. 69 ) formed in the proximal end of anvil retainer  610 . Openings  626  and  626   a  in retainer extension  608  and anvil retainer  610  ( FIG. 70 ), respectively, are dimensioned to receive pins or screws  628  ( FIG. 62 ) to secure anvil retainer  610  to the distal end of retainer extension  608 . Alternately, other attachment configurations and techniques are contemplated. 
         [0171]    Referring also to  FIGS. 69-71 , anvil retainer  610  includes an elongated reduced diameter distal extension  630  and a central annular shoulder  632 . In one embodiment, annular shoulder  632  defines an angle of about ninety-degrees with respect to the outer axial surface  610   a  of anvil retainer  610  ( FIG. 71 ). As will be discussed in further detail below, the sharp angle of shoulder  632  securely fastens an anvil assembly onto anvil retainer  610 . As discussed above with respect to stapling device  10 , when approximation knob  602  ( FIG. 62 ) is manually rotated, rotatable sleeve  604  is rotated about the proximal end of screw  606  to advance or retract screw  606  within handle assembly  601 . Since the proximal end  612  of retainer extension  608  is fastened to the distal end of screw  606  and the proximal end of anvil retainer  610  is fastened to the distal end of retainer extension  608 , retainer extension  608  and anvil retainer  610  will move axially within central body portion  603  when drive screw  606  moves axially within handle assembly  601 . As will be discussed in further detail below, an anvil assembly  640  ( FIG. 64 ) is secured to anvil retainer  610 . Accordingly, when approximation knob  602  is manually rotated, anvil assembly  640  will move axially with anvil retainer  610  in relation to a shell assembly  642  between spaced and approximated positions. 
         [0172]    As illustrated in  FIGS. 62-64 , distal head portion  605  ( FIG. 63 ) includes anvil assembly  640  and shell assembly  642 . Shell assembly  642  includes a housing  644 , a pusher  646 , a cylindrical knife  645  and a staple guide  648 . Referring also to  FIGS. 72-79 , housing  644  includes an outer housing portion  644   a  and an inner guide portion  644   b.  Outer housing portion  644   a  ( FIGS. 72-75 ) defines an outwardly diverging throughbore  650  and includes a small diameter proximal end  652  and a large diameter distal end  654 . Distal end  652  includes a pair of diametrically opposed spring tabs  656  for releasably engaging inner guide portion  644   b  in a manner to be discussed below. Throughbore  650  is dimensioned to slidably receive pusher  646  ( FIG. 62 ). Because of the configuration of throughbore  650  and pusher  646 , pusher  646  is slidable in throughbore  650  only in a distal direction. A pair of stabilizing ribs  653  ( FIG. 75 ) extend inwardly from an inner wall defining throughbore  650 . Stabilizing ribs  653  engage ribs  654  ( FIG. 76 ) formed on sidewalls of inner guide portion  644   b  to secure inner guide portion  644   b  within outer housing portion  644   a.    
         [0173]    Inner guide portion  644   b  ( FIGS. 76-79 ) includes a cylindrical proximal end  658 , a cylindrical central portion  660  and an inner distal portion  662 . Proximal end  658  includes a pair of openings  664  for engaging spring tabs (not shown) formed on handle assembly  612  for securing shell assembly  642  onto handle assembly  612 . Ribs  654  are formed on inner distal portion  662  of inner guide portion  644   b.  A pair of annular ribs  666  is formed in spaced relation on central portion  660 . Spring tabs  656  of outer housing portion  644   a  ( FIGS. 72-75 ) are positioned to snap fit into the space between ribs  666  to secure inner guide portion  644   b  to outer housing portion  644   a.  Inner distal portion  662  defines a cylindrical bore  668  for slidably receiving retainer extension  608  and anvil retainer  610  ( FIG. 62 ). Cylindrical bore  668  includes an annular array of ribs and grooves  676  for accurately circumferentially and axially aligning anvil assembly  640  and shell assembly  642  during approximation thereof. The proximal end of distal portion  662  extends proximally within central portion  660  to define therewith a pair of channels  670  ( FIG. 78 ). A proximal portion of channels  670  is dimensioned to slidably receive drive arms of a pusher link (not shown). The pusher link employed in this embodiment is similar to pusher link  74  discussed above with respect to stapling device  10  and will not be discussed in further detail herein. 
         [0174]    Referring to FIGS.  62  and  80 - 83 , pusher  646  is slidably positioned within shell assembly housing  644 . Pusher  646  includes a pair of proximal extensions  676  which extends through the distal end of channels  670  ( FIG. 78 ) formed in inner guide portion  644   b.  The distal end of pusher  646  includes a multiplicity of distally extending fingers  680  which are slidably received within slots formed in staple guide  648  ( FIG. 62 ). Staple guide  648  is fixedly retained in the distal end of outer housing portion  644   a . Staples (not shown) are housed within the staple guide slots (not shown). Movement of pusher  646  distally within outer housing portion  644   a  ejects staples from the slots of staple guide  648 . A cylindrical knife  645  ( FIGS. 62 and 63 ) is secured or frictionally retained within a central throughbore of pusher  646 . The distal end of knife  645  includes an annular cutting edge  682 . The distal portion of pusher  646  defines an internal chamber  780  for receiving excised tissue. 
         [0175]    Referring to  FIGS. 84-89 , anvil assembly  640  includes an anvil head assembly  684  and an anvil center rod  686 . Anvil head assembly  684  includes an anvil head  688 , an anvil post  690 , an anvil  692  and an anvil cover  694 . Anvil cover  694  ( FIGS. 91 and 92 ) is substantially conical and includes a rounded distal portion  696  to facilitate smooth entry of anvil assembly  640  into a body lumen or orifice, e.g., anus. Anvil  692  is secured to anvil head  688  and includes a plurality of staple deforming pockets (not shown), as discussed above, for receiving and deforming staples. Anvil head assembly  684  is secured to the distal end of anvil center rod  686 . Although anvil head assembly  684  may be pivotally secured to anvil center rod  686 , as discussed above, in one embodiment, anvil head assembly  684  is fixedly secured to anvil center rod  686 . 
         [0176]    As illustrated in  FIGS. 86 and 87  and  90 , anvil center rod  686  defines a central bore  700  which is partially defined by a plurality of flexile arms  702 . Central bore  700  extends substantially along the longitudinal length of center rod  686 . The distal end of each flexible arm  702  includes a radial projection  702   a.  Central bore  700  is dimensioned to slidably receive anvil retainer  610  ( FIG. 62 ) including distal extension  630  such that radial projections  702   a  snap over and engage annular shoulder  632  ( FIGS. 70 and 71 ) of anvil retainer  610  to secure anvil assembly  640  to anvil retainer  610 . Radial projection  702   a  ( FIG. 90 ) defines a perpendicular surface which abuts shoulder  632  to securely fasten anvil assembly  640  to anvil retainer  610  and substantially prevent inadvertent disengagement of anvil assembly  640  from anvil retainer  610 . When anvil assembly  640  is secured to anvil retainer  610 , distal extension  630  of anvil retainer  610  extends through central bore  700  along a substantial portion of the length of anvil center rod  686 . In one embodiment, distal extension  630  extends through central bore  700  substantially the entire length of anvil center rod  686 . 
         [0177]    In use, when approximation knob  602  ( FIG. 63 ) is manually rotated to move screw  606  proximally, anvil retainer  610  and anvil assembly  640  are withdrawn into shell assembly  642  to move anvil head assembly  684  into approximation with shell assembly  642  ( FIG. 65 ). When flexible arms  702  are drawn into cylindrical bore  668  of inner guide portion  644   b,  arms  702  are prevented from flexing outwardly to lock anvil assembly  640  to anvil retainer  610 . 
         [0178]    As discussed above, stapling device  600  is particularly suitable for use in surgical procedures for removing internal hemorrhoids from a patient. During such a procedure, anvil assembly  640  ( FIG. 64 ) is inserted into the anus and rectum of the patient independently of stapling device  600 . Referring to  FIGS. 93-95 , an insertion handle  720  may be used to facilitate insertion of anvil assembly  640  into the anus and rectum. In one embodiment, handle  720  includes a gripping knob  722 , a rigid shaft  725  extending distally from knob  722  and an attachment portion  724 . Attachment portion  724  includes a detent  726  and a protrusion  728 . Attachment portion  725  of shaft  724  is dimensioned to be slidably received within anvil center rod central bore  700 . Detent  726  is positioned to be received within one of a plurality of suture holes  730  ( FIG. 87 ) formed in the distal end of anvil center rod  686  to releaseably lock handle  720  to anvil center rod  686 . Protrusion  728  is positioned to be slidably received between and engaged by flexible arms  702  to properly align handle  720  with anvil center rod  686 . A stop member  728   a  may also be provided on the attachment portion to limit the insertion depth of shaft  724  into central bore  700 . To remove handle  720  from anvil center rod  686 , a force sufficient to flex flexible arms  702  outwardly must be applied to handle  720  to release detent  726  from suture hole  730 . In one embodiment, after anvil assembly  640  has been properly positioned in the anus and rectum, a purse string suture is placed into each of the internal hemorrhoids. Thereafter, the purse string is cinched about the anvil center rod  686  to draw the internal hemorrhoids inwardly about the anvil center rod  686 . 
         [0179]    Referring to  FIGS. 96-99 , in an alternate embodiment, the purse string suture may be placed into the internal hemorrhoids prior to insertion of the anvil assembly into the anus and rectum. Using either embodiment, an anoscope or speculum  750 , may be provided to place the purse string into the internal hemorrhoids. Speculum  750  may include a semi-cylindrical body  752  having a tapered or blunt tip  754 . Body  752  defines a channel or recess  756 . The proximal end of body  752  has a semi-annular flange  758  including a plurality of openings  760  and a pair of protruding finger tabs  762 . Fingers tabs  762  and openings  760  allow for easier gripping and manipulation of the speculum during use. It is also envisioned that speculum  750  may be formed from a clear plastic material to enhance visualization. Further, the speculum  750  may include gradation markings (not shown) along the surface of the speculum  750  to assist the surgeon with knowledge of depth of placement of the hemorrhoids. 
         [0180]    In use, blunt tip  754  of speculum  750  is inserted into the anus to a position in which first internal hemorrhoids hang into channel  756 . A purse string suture is placed into a first portion of internal hemorrhoids. Speculum  750  is then rotated using finger tabs  762  and openings  760  until a second portion of internal hemorrhoids hang into channel  756 . A purse string suture is placed into the second internal hemorrhoids. This process is repeated until a purse string suture has been placed into each of the internal hemorrhoids about the annulus of the anus. 
         [0181]    When a purse string suture has been placed into each of the internal hemorrhoids, speculum  750  is removed from the anus and the anvil assembly  640  is inserted into the anus and rectum. Thereafter, the purse string sutures are cinched to draw the internal hemorrhoids in about the anvil center rod  686 . Attachment structure such as openings, grooves, hooks, ridges or ribs, may be provided on anvil center rod  686  to secure the purse string suture and, thus, the internal hemorrhoids to the anvil center rod  686 . It is also envisioned that the attachment structure may be in the form of an axially adjustable member, e.g., slidable hook, which may be adjusted to change the position of the purse string suture on anvil center rod  686  and within shell assembly  642 . Likewise, gradations can be placed on the center rod  686  to indicate depth of insertion of the center rod  686  or length of the suture or of sutured hemorrhoids. 
         [0182]    After the internal hemorrhoids have been cinched about anvil center rod  686 , center rod  686  is attached to anvil retainer  610  in the manner discussed above. Distal extension  630  and anvil center rod  686  should be of a length to allow telescoping of extension  630  within anvil center rod  686  before visibility of the surgical site is obstructed by shell assembly  642  of device  600 . In one embodiment, the combined length of anvil center rod  686  and retainer extension  630  is at least 4.5 inches (114.3) or of a length to achieve the above objective. By providing an extension on anvil retainer  610  and/or providing an elongated anvil center rod  686 , visibility at the surgical site is greatly improved. Improved visibility not only simplifies attachment of anvil assembly  640  to anvil center rod  686  but improves visibility during approximation of anvil to ensure that the hemorrhoidal tissue is properly positioned about the anvil shaft. 
         [0183]    After the anvil assembly has been attached to the anvil center rod  686 , knob  602  can be manually rotated to approximate the anvil and shell assemblies and draw the internal hemorrhoids into an inner chamber  780  ( FIG. 62 ) defined within pusher  646  and within annular knife  682  of shell assembly  642 . Firing trigger  790  ( FIG. 62 ) can now be actuated in the manner discussed above with respect to stapling device  10  to staple, sever and allow removal of the internal hemorrhoids. Thereafter, stapling device  600  is removed from the anus with the excised internal hemorrhoids contained within inner chamber  780  of shell assembly  642 . 
         [0184]    It is envisioned that instrument accessories may be used to assist in performing particular steps of the above described procedures. For example, an anal dilator may be inserted into the anus prior to performing the above-described method steps to provide easier access to the surgical site. An obturator may be used to assist in placement of the dilator. Also, an expandable introducer may be provided to reduce the trauma that results from insertion of the stapling device into the anus. Further, any combination of the components discussed above including the stapling device, anvil assembly, insertion handle, speculum anal dilator, and/or an obturator may be included in a kit to perform a hemorrhoidal treatment procedure. 
         [0185]    It is noted that by providing a surgical stapler having a removable anvil assembly, visibility at the surgical site is greatly improved. This is especially important during placement of the purse string suture and cinching of the purse string suture about the anvil center rod. 
       Camera Assembly 
       [0186]    A camera assembly  30   a  will now be described with reference to  FIGS. 100-109 . The camera assembly  30   a  is configured and adapted to be operably coupled to the anvil head  124  of the anvil assembly  30 . In particular, at least part of the camera assembly  30   a  may have a shape, e.g., a dome shape, which approximates the shape of the surface of the anvil head  124 . The camera assembly  30   a  is placed at the distal surface of the anvil head  124  to provide forward viewing. The camera assembly  30   a  may be releasably or permanently affixed to the anvil head  124 . 
         [0187]    In the embodiment shown in  FIG. 109 , the camera assembly  30   a  includes an adhesive backing  30   d.  The adhesive backing  30   d  may be formed from an epoxy to removably bond the camera assembly  30   a  to the outer surface of the anvil head  124 . A removable liner  30   b  may cover the adhesive backing  30   d  prior to placement of the camera assembly  30   a  on the anvil head  124 . 
         [0188]    The camera assembly  30   a  includes a camera lens  30   c.  An internal power source for the camera assembly  30   a  may be provided. For example, the camera assembly  30   a  may be powered by a battery. In addition, the camera assembly  30   a  may wirelessly transmit images. Moreover, the camera assembly  30   a  may include a light source  30   e  ( FIG. 109 ) to illuminate the surgical site. In addition, the camera assembly  30   a  may wirelessly receive instructions from the surgeon including instructions to begin transmitting images and to activate the light source. 
         [0189]    As discussed above, during unapproximation of the stapling device  10  after the device  10  has been fired, the anvil head  124  tilts as the pivot member  164  pivots ( FIGS. 103-108 ). As the anvil head  124  tilts, the camera lens  30   c  also tilts. With the anvil head  124  in the tilted position, the camera lens  30   c  is directed towards the staple line facilitating viewing of the anastomosis prior to removal of the device  10  from the surgical site. Consequently, by providing the camera lens  30   c  on the tiltable anvil head, the staple line can be viewed to ensure proper sealing rather than requiring the separate steps of withdrawing the stapler and inserting an endoscope to check the quality of the staple line. 
         [0190]    It will be understood that various modifications may be made to the embodiments disclosed herein. Therefore, the above description should not be construed as limiting, but merely as exemplifications of disclosed embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.