Patent Description:
The present disclosure generally relates to a surgical stapling instrument and, more particularly, to a surgical anvil assembly for use with a circular stapling instrument and having an anvil head capable of pivoting or tilting to facilitate insertion and/or withdrawal of the anvil assembly relative to the operative site.

Circular stapling instruments for performing surgical procedures such as anastomoses, hemorrhoidectomies, and mucosectomies are well known. These devices include an anvil assembly having a center rod and an anvil head supported on the center rod. Typically, during a surgical procedure, the tool assembly of the circular stapling instrument is inserted into a tubular section or sections of tissue to join the tissue sections or remove diseased or damaged tissue from within the tissue section. In order to minimize trauma to the tissue section, the anvil head may be pivotally supported on the center rod to reduce the profile of the anvil assembly during insertion and/or removal of the tool assembly from the tissue section. In some circular stapling instruments a component is fractured during firing to permit tilting of the anvil head relative to the center rod.

<CIT> discloses an anvil assembly including a retaining member having a body portion and a frangible portion connected to the body portion, where the frangible portion is positioned to engage a backup member and separates from the body portion during movement of the backup member from a first, proximal position to a second, distal position. The retaining member keeps the backup plate in the proximal position prior to firing of the stapling assembly, and upon separation of the frangible portion allows the backup plate to move to the distal position during firing of the stapling assembly. Proximal force on the backup plate after firing of the stapling assembly is avoided, thereby helping to ensure titling of the anvil assembly.

Further embodiment are provided by the dependent claims.

in one aspect of the present disclosure, a surgical anvil assembly for use with a circular stapling instrument is provided and includes an anvil center rod, an anvil head pivotally coupled to the anvil center rod and movable between a first, operative condition and a second, tilted condition, a backup member slidably disposed within a recess of the anvil head and selectively engagable with the anvil center rod, and a locking assembly. The locking assembly includes an inner member supported on an outer surface of the anvil head, an outer member movably coupled to the inner member, and a post interconnecting the outer member and the backup member. The outer member is configured to move relative to the inner member between a first, proximal position, in which the locking assembly maintains the backup member engaged with the anvil center rod to resist movement of the anvil head relative to the anvil center rod, and a second, distal position, in which the locking assembly maintains the backup member disengaged from the anvil center rod to allow for movement of the anvil head relative to the anvil center rod.

In some aspects, the locking assembly may further include a locking member protruding outwardly from the inner member. The locking member may be configured to engage the outer member when the outer member is in the second, distal position to maintain the outer member in the second, distal position and, in turn, maintain the backup member disengaged from the anvil center rod.

The locking member may be configured to prevent movement of the backup member from the first, proximal position toward the second, distal position until a threshold, distally-oriented force has been applied to the backup member.

In some aspects, the locking member may overlap with an inner lip of the outer member to resist distal movement of the outer member relative to the inner member toward the second, distal position.

The locking member may include a first locking member extending radially outward from a first side of the inner member, and a second locking member extending radially outward from a second side of the inner member. The first and second locking members may be engagable with an inner periphery of the outer member.

In some aspects, the locking member may include a detent configured to engage an inner periphery of the outer member when the outer member is in the second, distal position.

The outer member may include a lip protruding radially inwardly from the inner periphery thereof. The lip may be disposed proximally of the detent when the outer member is in the first, proximal position, such that the detent resists movement of the outer member from the first, proximal position toward the second, distal position. The lip may be aligned with the detent when the outer member is in the second, distal position, such that the detent resists movement of the outer member from the second, distal position toward the first, proximal position.

In some aspects, the detent may be configured to move radially inward upon movement of the outer member toward the second, distal position. The detent may be configured to move radially outward upon movement of the outer member toward the first, proximal position.

The post may have a distal end disposed outside of the anvil head, an intermediary portion extending through the anvil head, and a proximal end disposed within the recess of the anvil head.

In some aspects, the anvil center rod may have a pair of arms supporting the backup member thereon when the backup member is in the first, proximal position, such that the pair of arms prevent the backup member from pivoting relative thereto.

The surgical anvil assembly further includes a cut ring positioned about the backup member and secured thereto.

In some aspects, the surgical anvil assembly may further include a cam latch mounted to a post of the anvil head. The cam latch may be configured to normally bias the anvil head to the second, tilted condition.

Other features of the present disclosure will be appreciated from the following description.

Various embodiments of the presently disclosed surgical anvil assemblies for incorporation into surgical circular stapling instruments are described herein below with reference to the drawings, wherein:.

The presently disclosed anvil assemblies for use with various circular stapling instruments 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. In this description, the term "proximal" is used generally to refer to that portion of the instrument or surgical anvil assembly thereof that is closer to a clinician, while the term "distal" is used generally to refer to that portion of the instrument or surgical anvil assembly thereof that is farther from the clinician. In addition, the term clinician is used generally to refer to medical personnel including doctors, nurses, and support personnel.

The exemplary surgical stapling instrument includes a handle assembly, an elongate body or adapter, and a tool assembly coupled to the adapter. The tool assembly includes a shell assembly and an anvil assembly mounted with respect to the shell assembly. The anvil assembly includes a center rod releasably couplable to the elongate body and an anvil head which is pivotally coupled to the center rod. The anvil head is movable between a pre-fired, untilted or operative condition and a post-fired, tilted or pivoted condition. The anvil head is locked in the pre-fired position until an annular knife of the tool assembly is advanced, which frees the anvil head to pivot or rotate relative to the center rod towards the pivoted condition. The present disclosure provides, inter alia, various embodiments of mechanisms for unlocking the anvil head from the anvil center rod, and various embodiments of mechanisms that drive the rotation of the anvil head upon being unlocked from the center rod.

Referring initially to <FIG>, an exemplary embodiment of a circular stapling instrument for incorporating the surgical anvil assemblies of the present disclosure is illustrated and shown generally as circular stapling instrument <NUM>. The circular stapling instrument <NUM> includes a handle <NUM>, an elongate body or adapter <NUM> extending from the handle <NUM>, and a tool assembly <NUM> coupled to the adapter <NUM>. The handle <NUM> may be electrically powered including a motor and associated gears and linkages to control operation of the stapling instrument <NUM>. The handle <NUM> incorporates a grip <NUM> and a plurality of actuation buttons <NUM> which may be activated to control various functions of the stapling instrument <NUM> including, e.g., approximation of the tool assembly <NUM> and firing of staples. The grip <NUM> may support a battery pack (not shown) which powers the handle <NUM>. In embodiments, the circular stapling instrument <NUM> may be powered via an external power source.

In embodiments, the adapter <NUM> is releasably coupled to the handle <NUM> and includes a plurality of drive mechanisms (not shown) that translate power from the handle <NUM> to the tool assembly <NUM> in response to actuation of the actuation buttons <NUM> to effect operation, e.g., approximation and firing, of the tool assembly <NUM>. The adapter <NUM> also includes an anvil retainer <NUM> or trocar that extends from a distal portion of the adapter <NUM> and is movable between retracted and advanced positions. The anvil retainer <NUM> is couplable to the tool assembly <NUM>. Commonly assigned <CIT>; <CIT>; and <CIT>, and <CIT> disclose exemplary embodiments of powered handles and adapters suitable for use with the stapling instrument <NUM> Alternately, the elongate body or adapter <NUM> may be non-removably secured to the handle <NUM>.

It is also envisioned that the handle <NUM> may be manually powered. Examples of manually powered handle assemblies are described in commonly assigned <CIT>; <CIT>; and <CIT>.

Referring to <FIG>, in conjunction with <FIG>, the tool assembly <NUM> includes a shell <NUM> and a surgical anvil assembly <NUM> releasably mounted to the shell <NUM>. The shell <NUM> supports an annular staple cartridge <NUM> and an annular knife <NUM> internal of the staple cartridge <NUM>. The staple cartridge <NUM> includes a plurality of staple receptacles <NUM> each accommodating an individual staple <NUM> and a staple pusher <NUM> for ejecting the staples <NUM> from the staple cartridge <NUM> upon firing of the instrument <NUM>.

The anvil assembly <NUM> shares common features with the anvil assembly disclosed in commonly assigned <CIT>. As best depicted in <FIG>, the anvil assembly <NUM> includes an anvil center rod <NUM> and an anvil head <NUM> pivotally mounted to the anvil center rod <NUM>. The anvil head <NUM> is adapted to pivot between a first operative condition as depicted in <FIG> and <FIG>, and a second pivoted or tilted condition as depicted in <FIG>. The anvil center rod <NUM> includes a pair of distal spaced arms <NUM> having transverse bores <NUM> that receive a pivot member, such as, for example, a pivot pin <NUM>, therethrough. The anvil head <NUM> is pivotably coupled to the distal spaced arms <NUM> via the pivot pin <NUM>.

The anvil assembly <NUM> further includes a plunger <NUM>, a plunger spring <NUM>, and a cam latch or cam plate <NUM>. The plunger <NUM> is at least partially received within the anvil center rod <NUM>, e.g., between the spaced arms <NUM>, and is spring biased in a distal direction by the plunger spring <NUM>. The plunger <NUM> includes a plunger finger <NUM>, which engages the cam latch <NUM> to provide a distally-oriented force on the cam latch <NUM>.

The anvil head <NUM> includes a housing <NUM> defining a recess <NUM> therein, and a post <NUM> extending proximally from a center of the housing <NUM>. The housing <NUM> has an anvil tissue contact surface <NUM> defining a plurality of staple deforming pockets <NUM>. The post <NUM> of the anvil head <NUM> includes a pair of spaced post arms <NUM> defining a slot <NUM> and transverse bores <NUM> extending through the spaced post arms <NUM>. As briefly mentioned above, the anvil center rod <NUM> is at least partially positioned about the post <NUM> and coupled to the anvil head <NUM> through the pivot member <NUM> which extends through respective transverse bores <NUM>, <NUM> of the distal spaced arms <NUM> of the anvil center rod <NUM> and the post <NUM> to pivotally couple the anvil head <NUM> to the anvil center rod <NUM>. In addition, the cam latch <NUM> is received within the slot <NUM> of the post <NUM> and coupled to the anvil center rod <NUM> and the post <NUM> via the pivot member <NUM> which extends through a pin opening <NUM> of the cam latch <NUM>.

Referring now to <FIG>, the anvil assembly <NUM> further includes a backup member <NUM> and a cut ring <NUM> attached thereto. The backup member <NUM> and the cut ring <NUM> are moved together within the recess <NUM> of the anvil head <NUM> upon application of a force thereto, e.g., during advancement of the annular knife <NUM> of the tool assembly <NUM> during firing of the instrument <NUM>. The backup member <NUM> includes an annular body <NUM> and a pair of diametrically opposed fingers <NUM> extending radially inward from the annular body <NUM>. The annular body <NUM> of the backup member <NUM> is axially movable, but pivotally fixed within the recess <NUM> of the anvil head <NUM>.

The fingers <NUM> are engaged by the spaced arms <NUM> of the anvil center rod <NUM> to prevent the backup member <NUM> from moving in a proximal direction and to maintain the anvil head <NUM> in the operative condition (e.g., untilted) until the annular knife <NUM> is actuated. More specifically, when the backup member <NUM> is in the proximal position, as shown in <FIG>, the fingers <NUM> of the backup member <NUM> sit on or abut a distal surface of the spaced arms <NUM> of the anvil center rod <NUM>, whereby rocking or pivotal movement of the anvil head <NUM> relative to the anvil assembly <NUM> is prevented. Pivotal movement of the anvil head <NUM> relative to the anvil center rod <NUM> is permitted only after the fingers <NUM> are distally spaced from the arms <NUM> of the anvil center rod <NUM>.

The backup member <NUM> further includes a pair of diametrically opposed cam shelves <NUM> extending radially inward from the annular body <NUM>. The cam shelves <NUM> capture the cam latch <NUM> therebetween to rotationally fix the cam latch <NUM> to the backup member <NUM>. In this way, as the cam latch <NUM> rotates or pivots, so does the backup member <NUM> and the anvil head <NUM> as a whole. The backup member <NUM> may be formed from a hard material such as metal, although other materials of construction are envisioned.

The cut ring <NUM> of the anvil assembly <NUM> includes a disc-shaped annular body <NUM> defining a central aperture <NUM> for reception of the backup member <NUM>. Thus, movement of the backup member <NUM> between the untilted and tilted conditions causes corresponding movement of the cut ring <NUM>. In embodiments, the cut ring <NUM> may be formed through a molding process, e.g., an injection molding process, and may be fabricated from a material having a durometer which permits the annular knife <NUM> to pierce through the annular body <NUM> and bottom out against the backup member <NUM>. Suitable materials of the cut ring <NUM> include polypropylene or polyester. Other materials are contemplated.

Prior to firing of the stapling instrument <NUM>, the backup member <NUM> is in its retracted or proximal position with the cut ring <NUM> secured to the backup member <NUM> in the aforedescribed manner. With the backup member <NUM> in the proximal position, the inwardly extending fingers <NUM> of the backup member <NUM> are engaged by the spaced arms <NUM> (<FIG>) of the anvil center rod <NUM>, such that the anvil head <NUM> is retained in the operative condition. As described above, the plunger finger <NUM> of the plunger <NUM> of the anvil center rod <NUM> is positioned to urge the cam latch <NUM> and the anvil head <NUM> about the pivot member <NUM> towards the tilted condition (<FIG>). However, the anvil head <NUM> is prevented from pivoting until the annular knife <NUM> is advanced to unlock a locking assembly <NUM> (<FIG>, and <FIG>) of the surgical anvil assembly <NUM>, as will be described.

With reference to <FIG>, the surgical anvil assembly <NUM> may further include a locking assembly <NUM> for selectively locking the anvil head <NUM> in each of the first, operative condition, and the second, tilted condition. The locking assembly <NUM> replaces the deformable retainer members of the prior art, such as the retainer member <NUM> described in <CIT>. The deformable retainer members typically support the backup member <NUM> in the proximal position and deform upon advancement of the backup member <NUM> to allow for tilting of the anvil head <NUM>. Due to the absence of the deformable retainer in the present embodiment, the anvil head <NUM> is capable of repeated movement between the untilted and tilted conditions.

The locking assembly <NUM> generally includes an annular inner member or housing <NUM>, an annular outer member <NUM> surrounding the inner member <NUM>, and a pair of locking elements 106a, 106b movably coupled to the inner member <NUM>. In embodiments, the inner and outer members <NUM>, <NUM> may assume any suitable shape, such as, for example, ring-shaped, squared, triangular, or the like. The inner member <NUM> is fixedly supported on a distally-facing outer surface <NUM> of the anvil head <NUM>. The anvil head <NUM> may have a plurality of holes <NUM> (<FIG>) defined therethrough for receipt of fasteners (not explicitly shown) that fixedly attach the inner member <NUM> of the locking assembly <NUM> to the anvil head <NUM>. The inner member <NUM> defines a plurality of passageways <NUM> defined transversely therethrough for housing a respective locking element 106a or 106b. While four passageways <NUM> are illustrated, it is contemplated that the inner member <NUM> may have more or less than four passageways <NUM> for accommodating a respective number of locking elements 106a, 106b.

The locking elements 106a, 106b are received in the passageways <NUM> of the inner member <NUM> and are arranged in diametrical opposition to one another. The locking elements 106a, 106b may be ball detents that protrude radially outward from an outer periphery <NUM> of the inner member <NUM>. In embodiments, the locking elements 106a, 106b may be any suitable biasing member that is resiliently, radially-outwardly biased. In embodiments, the locking elements 106a, 106b may remain fixed relative to the inner member <NUM> whereas the outer member <NUM> may be flexible, such that the outer member <NUM> flexes outwardly upon contacting the locking element 106a, 106b as the outer member <NUM> slides along the inner member <NUM>, as will be described.

The outer member <NUM> of the locking assembly <NUM> surrounds the inner member <NUM> and is slidable relative thereto along a longitudinal axis "X" between a first, proximal position (<FIG>), in which the outer member <NUM> abuts the outer surface <NUM> of the anvil head <NUM>, and a second, distal position (<FIG>), in which the outer member <NUM> is distally spaced from the outer surface <NUM> of the anvil head <NUM>. The outer member <NUM> has an inner surface or inner periphery <NUM> that is adjacent to and surrounds the outer periphery <NUM> of the inner member <NUM>. The inner periphery <NUM> of the outer member <NUM> has a lip or ledge <NUM> protruding radially inward therefrom for selective interaction with the locking elements 106a, 106b.

More particularly, in the first, proximal position (<FIG>), the lip <NUM> of the outer member <NUM> is disposed proximally of an outer surface of the locking elements 106a, 106b while also overlapping therewith. Due to the lip <NUM> of the outer member <NUM> overlapping the locking elements 106a, 106b, the locking elements 106a, 106b resist distal movement of the outer member <NUM> relative to the inner member <NUM>. To distally move the outer member <NUM> of the locking assembly <NUM>, a threshold force oriented in the distal direction must be applied to the outer member <NUM> to overcome the spring force of the locking elements 106a, 106b. Upon application of the threshold force, the locking elements 106a, 106b are moved radially inward relative to the inner member <NUM>, allowing the lip <NUM> of the outer member <NUM> to pass over the locking elements 106a, 106b.

When the outer member <NUM> is in the second, distal position (<FIG>), the locking elements 106a, 106b and the lip <NUM> of the outer member <NUM> are engaged and aligned along a transverse axis. Since the locking elements 106a, 106b exhibit an outwardly-oriented spring bias, the lip <NUM> of the outer member <NUM> and the locking elements 106a, 106b are frictionally engaged with one another, thereby resisting movement of the outer member <NUM> from the second, distal position until the threshold force is applied in the proximal direction.

The locking assembly <NUM> further includes a plurality of posts or rods <NUM> interconnecting the inner member <NUM> of the locking assembly <NUM> and the backup member <NUM>. The posts <NUM> are circumferentially spaced from one another and extend downwardly (e.g., proximally) from the outer member <NUM>. The posts <NUM> have a distal end 118b attached to or formed with the outer member <NUM>, an intermediary portion 118c extending through a respective hole <NUM> defined through the anvil head <NUM>, and a proximal end 118a disposed within the recess <NUM> of the anvil head <NUM>. The proximal end 118a of each of the posts <NUM> is fixed to the backup member <NUM>, such that the backup member <NUM> moves with the outer member <NUM> as the outer member <NUM> moves relative to the inner member <NUM>. Accordingly, as the outer member <NUM> moves from the first, proximal position (<FIG>) toward the second, distal position (<FIG>), the backup member <NUM> moves deeper into the recess <NUM> of the anvil head <NUM> and out of engagement with the distal spaced arms <NUM> of the anvil center rod <NUM>.

In operation, the backup member <NUM> with the cut ring <NUM> is maintained in the recess <NUM> in the proximal position by the locking assembly <NUM>. In particular, the locking elements 106a, 106b resist distal movement of the outer member <NUM> of the locking assembly <NUM> relative to the inner member <NUM> of the locking assembly <NUM>. Since the backup member <NUM> is fixed to the outer member <NUM> via the posts <NUM> of the locking assembly <NUM>, distal movement of the backup member <NUM> toward the distal position is also resisted.

When the anvil head <NUM> and the staple cartridge <NUM> (<FIG>) of the shell <NUM> are approximated, the stapling instrument <NUM> may be fired to advance the annular knife <NUM> within the shell <NUM> from a retracted position recessed within the shell <NUM> to an advanced position extending into the cut ring <NUM> of the anvil assembly <NUM>. As the annular knife <NUM> engages the cut ring <NUM>, the cut ring <NUM> and the backup member <NUM> exert a distally-oriented force on the outer member <NUM> of the locking assembly <NUM> via the posts <NUM> of the locking assembly <NUM>. Upon applying the threshold force on the outer member <NUM>, the locking element(s) 106a, 106b are forced radially-inward into the respective passageways <NUM> of the inner member <NUM>, allowing the lip <NUM> of the outer member <NUM> to pass over the locking elements 106a, 106b as the backup member <NUM> is advanced to the second, distal position within the recess <NUM> of the anvil head <NUM>, as shown in <FIG>. Once the backup member <NUM> moves towards its second position, the lip <NUM> of the outer member <NUM> and the locking elements 106a, 106b frictionally engage one another to selectively fix the outer member <NUM> and, in turn, the backup member <NUM> in the second, distal position.

As the backup member <NUM> is moved toward its distal position, the fingers <NUM> (<FIG>) of the backup member <NUM> disengage the distal spaced arms <NUM> of the anvil center rod <NUM>, freeing the anvil head <NUM> to pivot relative to the anvil center rod <NUM>. With the anvil head <NUM> free to rotate, the plunger spring <NUM> (<FIG>) urges the plunger <NUM> in a distal direction whereby the plunger finger <NUM> engages the cam latch <NUM> to rotate the cam latch <NUM> and the anvil head <NUM> about the pivot member <NUM> to permit the anvil head <NUM> to assume the second tilted condition depicted in <FIG>.

After the anvil head <NUM> is moved to the tilted condition, the anvil head <NUM> may be manually moved back towards the first, operative condition. After moving the anvil head <NUM> back to the first, operative condition (e.g., untilted), the backup member <NUM> may also be reset to its proximal position. To move the backup member <NUM> to the proximal position, a proximally-oriented threshold force may be manually applied to the outer member <NUM> of the locking assembly <NUM>, which overcomes the static friction between the lip <NUM> of the outer member <NUM> and the locking elements 106a, 106b, whereby the outer member <NUM> moves proximally relative to the inner member <NUM>. Due to the interconnection between the outer member <NUM> and the backup member <NUM> via the posts <NUM>, the backup member <NUM> moves proximally with the outer member <NUM> back toward the proximal position.

Upon re-entering the proximal position, the fingers <NUM> (<FIG>) of the backup member <NUM> re-engage the distal spaced arms <NUM> of the anvil center rod <NUM>, thereby stabilizing the anvil head <NUM> in the first, operative condition. It is contemplated that this process of selectively moving the anvil head <NUM> relative to the anvil center rod <NUM> may be repeated indefinitely.

With reference to <FIG>, another embodiment of a surgical anvil assembly <NUM> is illustrated, similar to the anvil assembly <NUM> described above. Due to the similarities between the anvil assembly <NUM> of the present embodiment and the anvil assembly <NUM> described above, only those elements of the anvil assembly <NUM> deemed necessary to elucidate the differences from anvil assembly <NUM> will be described in detail.

With specific reference to <FIG> and <FIG>, the anvil assembly <NUM> includes an anvil center rod <NUM> and an anvil head <NUM>, similar to the anvil head <NUM> described above. The anvil head <NUM> is pivotally mounted to the anvil center rod <NUM>. The anvil center rod <NUM> may include a pair of distal spaced arms <NUM> and an elongated proximal body portion <NUM> extending proximally from the pair of distal spaced arms <NUM>. The distal spaced arms <NUM> define transverse bores <NUM> through a distal end thereof for receiving a pivoting member (not explicitly shown), similar to the pivot member <NUM> described above. The proximal body portion <NUM> of the anvil center rod <NUM> is configured to releasably couple to an anvil retainer or trocar, such as, for example, the anvil retainer <NUM> shown in <FIG>. A detailed description of an anvil retainer may be found in <CIT>.

The proximal body portion <NUM> of the anvil center rod <NUM> defines a pair of diametrically opposed slots 150a, 150b. The slots 150a, 150b extend proximally from a location adjacent a proximal end of the distal spaced arms <NUM> and terminate distally of a proximal end of the proximal body portion <NUM>. The slots 150a, 150b are dimensioned for receipt of a pair of legs <NUM>, <NUM> configured to releasably capture the anvil retainer <NUM> therebetween, as will be described below.

With reference to <FIG>, the legs <NUM>, <NUM> of the anvil center rod <NUM> are received within a respective slot 150a, 150b in the proximal body portion <NUM> of the anvil center rod <NUM>. Each of the legs <NUM>, <NUM> is fabricated from a material that allows the legs <NUM>, <NUM> to flex about proximal ends 152a, 154a thereof in a spring-like manner. It is contemplated that the thickness of the legs <NUM>, <NUM> may be increased or decreased to adjust the flexibility thereof. Distal ends 152b, 154b of the legs <NUM>, <NUM> are attached to an inner periphery <NUM> of the proximal body portion <NUM> via, for example, laser welding, whereas proximal ends 152a, 154a of the legs <NUM>, <NUM> are free to pivot relative to the respective distal end 152b, 154b.

In embodiments, the legs <NUM>, <NUM> may be attached to the proximal body portion <NUM> along any suitable location of the legs <NUM>, <NUM> using any suitable fastening method. As can be appreciated, adjusting the location at which the legs <NUM>, <NUM> are attached to the proximal body portion <NUM> changes the force required to flex the legs <NUM>, <NUM>. The proximal ends 152a, 154a of the legs <NUM>, <NUM> include a tab or detent <NUM>, <NUM> that extends radially inward. The detents <NUM>, <NUM> are configured for snap fit engagement with a lip <NUM> defined by a proximal end of the trocar <NUM>, as will be described in further detail below.

Each of the legs <NUM>, <NUM> has an outer profile that matches the outer profile of the proximal body portion <NUM> so that the legs <NUM>, <NUM> do not protrude outwardly from the proximal body portion <NUM>. Each of the legs <NUM>, <NUM> has an inner profile that substantially matches an outer profile of the trocar <NUM>. As such, when the legs <NUM>, <NUM> are disposed within the respective slots 150a, 150b of the proximal body portion <NUM>, the legs <NUM>, <NUM> cooperatively define a cavity <NUM> therebetween dimensioned for receipt of the trocar <NUM>.

During manufacture, the legs <NUM>, <NUM> are received within a respective slot 150a, 150b of the proximal body portion <NUM>, and the distal end 152b, 154b of each of the legs <NUM>, <NUM> is welded (e.g., laser welded) to the inner periphery <NUM> (<FIG>) of the proximal body portion <NUM>. As shown in <FIG>, the trocar <NUM> is distally advanced, in the direction indicated by arrows "A" in <FIG>, through the proximal body portion <NUM>, whereby a tapered outer surface <NUM> of the base of the trocar <NUM> engages the detents <NUM>, <NUM> at the proximal end 152a, 154a of the legs <NUM>, <NUM>, causing the legs <NUM>, <NUM> to flex outwardly. As shown in <FIG>, distal advancement of the trocar <NUM> is continued until the lip <NUM> defined at the base of the trocar <NUM> passes over the detents <NUM>, <NUM> of the legs <NUM>, <NUM>, such that the detents <NUM>, <NUM> snap into place proximally of the lip <NUM> of the trocar <NUM>, capturing the trocar <NUM> in the cavity <NUM> defined between the legs <NUM>, <NUM>. The inwardly-oriented resilient bias of the legs <NUM>, <NUM> axially fixes the trocar <NUM> within the proximal body portion <NUM>.

With reference to <FIG>, another embodiment of a surgical anvil assembly <NUM> is illustrated, similar to the anvil assemblies described above. Due to the similarities between the anvil assembly <NUM> of the present embodiment and the anvil assemblies described above, only those elements of the anvil assembly <NUM> deemed necessary to elucidate the differences from the other anvil assemblies will be described in detail.

The anvil assembly <NUM> includes an anvil center rod <NUM>, an anvil head <NUM> pivotally mounted to the anvil center rod <NUM>, and a ring assembly <NUM> for selectively unlocking the anvil head <NUM> from the anvil center rod <NUM>. The anvil head <NUM> is configured to pivot relative to the anvil center rod <NUM> between a first operative condition and a second pivoted or tilted condition. The anvil head <NUM> defines a recess <NUM> therein having a post <NUM> of the anvil head <NUM> extending proximally therefrom. The post <NUM> of the anvil head <NUM> is pivotally coupled to a distal end of the anvil center rod <NUM>.

The ring assembly <NUM> is received within the recess <NUM> defined in the anvil head <NUM> and generally includes a backup member <NUM> and a cut ring <NUM> disposed about and secured to the backup member <NUM>. The ring assembly <NUM> is movable within the recess <NUM> of the anvil head <NUM> upon application of a force thereto, e.g., during advancement of an annular knife, such as, for example, the annular knife <NUM> shown in <FIG> and <FIG>. The backup member <NUM> of the ring assembly <NUM> has a ring body <NUM> and an annular lip <NUM> extending radially outward from a distal end of the ring body <NUM> to support the cut ring <NUM> thereon. The ring body <NUM> defines a central opening <NUM> for reception of the post <NUM> of the anvil head <NUM>. The central opening <NUM> is dimensioned to allow movement of the backup member <NUM> about the post <NUM> from a pre-fired, retracted or proximal position (<FIG>) to a post-fired, advanced or distal position (<FIG>) within the recess <NUM> of the anvil head <NUM>.

The backup member <NUM> further includes a pair of diametrically opposed fingers <NUM> extending inwardly from the ring body <NUM> into the central opening <NUM>. The fingers <NUM> are engaged by a distal end of the anvil center rod <NUM> to prevent the backup member <NUM> from moving in a proximal direction and to maintain the anvil head <NUM> in the operative condition (e.g., untilted), in a similar manner described above. Pivotal movement of the anvil head <NUM> relative to the anvil center rod <NUM> is permitted only after the fingers <NUM> are distally spaced from the distal end of the anvil center rod <NUM>. The backup member <NUM> is restricted from moving distally out of the proximal position by a frangible portion <NUM> of the cut ring <NUM>, as will be described below. The backup member <NUM> may be formed from a hard material such as metal, although other materials of construction are envisioned.

The cut ring <NUM> of the ring assembly <NUM> includes a disc-shaped annular body <NUM> defining a central aperture <NUM> for reception of the backup member <NUM>. The annular body <NUM> may be press fit onto the backup member <NUM>. Thus, movement of the backup member <NUM> between proximal and distal positions causes corresponding movement of the cut ring <NUM>. In embodiments, the cut ring <NUM> may be formed through a molding process, e.g., an injection molding process, and may be fabricated from a material having a durometer which permits the annular knife <NUM> to pierce through the annular body <NUM> and bottom out against the annular lip <NUM> of the backup member <NUM>. In embodiments, the cut ring <NUM> may be fabricated from a material that prevents advancement of the annular knife <NUM> therethrough and is instead coated with a material that permits advancement of the annular knife <NUM> therethrough. Suitable materials for the cut ring <NUM> include polytetrafluoroethylene, polypropylene or polyester. Other materials are contemplated.

As best shown in <FIG>, the cut ring <NUM> includes a plurality of pockets <NUM> formed in a bottom or proximal surface <NUM> thereof. The pockets <NUM> are illustrated as having a curved shape, but it is contemplated that the pockets <NUM> may assume any suitable shape. The cut ring <NUM> further includes a plurality of frangible portions or legs <NUM> extending distally from a top or distal surface <NUM> of the annular body <NUM> of the cut ring <NUM>. As shown in <FIG>, the frangible legs <NUM> suspend the annular body <NUM> of the cut ring <NUM> in the recess <NUM> of the anvil head <NUM> to maintain the ring assembly <NUM> in the proximal position. The frangible legs <NUM> may have a curved shape and are positioned directly over a respective pocket <NUM>. The frangible legs <NUM> are configured to deform (e.g., collapse) into the respective pocket <NUM> upon application of a distally-oriented threshold force on the ring assembly <NUM>.

To facilitate deformation of the frangible legs <NUM>, the distal surface <NUM> of the annular body <NUM> of the cut ring <NUM> defines a pair of annular indentations <NUM> disposed on opposite sides of the frangible legs <NUM>. The indentations <NUM> may have an arcuate, V-shaped, or any suitable cross-sectional configuration. The frangible legs <NUM> of the cut ring <NUM> may be fabricated from the same or a different material as the annular body <NUM> of the cut ring <NUM>. For example, the frangible legs <NUM> may be fabricated from polytetrafluoroethylene, polypropylene or polyester.

In operation, prior to firing of the annular knife <NUM> (<FIG> and <FIG>), the ring assembly <NUM> (including the backup member <NUM> and the cut ring <NUM>) is in its retracted or proximal position. In the proximal position, the frangible legs <NUM> of the cut ring <NUM> are in engagement with an inner surface <NUM> of the anvil head <NUM>, thereby maintaining the ring assembly <NUM> in the proximal position, as shown in <FIG>. With the ring assembly <NUM> in the proximal position, the inwardly extending fingers <NUM> of the backup member <NUM> are engaged by the anvil center rod <NUM>, such that the anvil head <NUM> is retained in the first, operative condition and prevented from pivoting relative to the anvil center rod <NUM>.

When the annular knife <NUM> (<FIG> and <FIG>) is advanced, the annular knife <NUM> engages the annular body <NUM> of the cut ring <NUM> of the ring assembly <NUM>. The annular knife <NUM> pierces the annular body <NUM> of the cut ring <NUM> and ultimately engages the annular lip <NUM> of the backup member <NUM>. The force applied by the annular knife <NUM> on the ring assembly <NUM> is transferred to the frangible legs <NUM> of the cut ring <NUM>, which are compressed between the annular body <NUM> of the cut ring <NUM> and the inner surface <NUM> of the anvil head <NUM>. Upon the annular knife <NUM> applying a distally-oriented threshold force on the ring assembly <NUM>, the frangible legs <NUM> of the cut ring <NUM> detach or break from the annular body <NUM> of the cut ring <NUM> along the annular indentations <NUM>.

With the frangible legs <NUM> of the cut ring <NUM> detached from the annular body <NUM> of the cut ring <NUM>, a continued distally-oriented force on the ring assembly <NUM>, applied via the annular knife <NUM>, drives the annular body <NUM> of the cut ring <NUM> and the backup member <NUM> distally, whereby the frangible legs <NUM> of the cut ring <NUM> collapse or fall into the respective pockets <NUM> in the annular body <NUM> of the cut ring <NUM>, as shown in <FIG>. As the ring assembly <NUM> is advanced toward the distal position, the inwardly extending fingers <NUM> of the backup member <NUM> disengage from the arms of the anvil center rod <NUM>, allowing for the anvil head <NUM> to pivot relative to the anvil center rod <NUM>. It is contemplated that the anvil head <NUM> may pivot automatically relative to the anvil center rod <NUM> in the same manner described above. In embodiments, the anvil head <NUM> may be pivoted automatically or manually via any suitable mechanism, such as those mechanisms described in the patents cited herein.

With reference to <FIG>, another embodiment of a surgical anvil assembly <NUM> is illustrated, similar to the surgical anvil assemblies described above. Due to the similarities between the anvil assembly <NUM> of the present embodiment and the anvil assemblies described above, only those elements of the anvil assembly <NUM> deemed necessary to elucidate the differences from the previously described anvil assemblies will be described in detail.

The anvil assembly <NUM> generally includes an anvil center rod (not shown), similar to the anvil center rods described above, an anvil head <NUM> configured to be pivotally mounted to the anvil center rod, and a ring assembly <NUM> configured to selectively unlock the anvil head <NUM> from the anvil center rod. The anvil head <NUM> is configured to pivot relative to the anvil center rod between a first operative condition and a second pivoted or tilted condition.

The anvil head <NUM> defines a recess <NUM> (<FIG>) therein having a post <NUM> of the anvil head <NUM> extending proximally therefrom. The post <NUM> of the anvil head <NUM> is configured to be pivotally coupled to a distal end of the anvil center rod. The recess <NUM> of the anvil head <NUM> is dimensioned for slidable receipt of the ring assembly <NUM>. The anvil head <NUM> includes an annular, inner peripheral surface <NUM> that partially defines the recess <NUM>, and an inner race or catch <NUM> that extends radially inward from the inner peripheral surface <NUM>. The inner race <NUM> resists, without preventing, distal movement of the ring assembly <NUM> through the recess <NUM> of the anvil head <NUM>.

The ring assembly <NUM> generally includes a backup member <NUM>, similar to the backup members described above, a ring cup <NUM> nested in the backup member <NUM>, and a cut ring <NUM> nested in the ring cup <NUM>. The ring assembly <NUM> is moved within the recess <NUM> of the anvil head <NUM> upon application of a force thereto, e.g., during advancement of an annular knife <NUM> (<FIG>). The backup member <NUM> defines a central opening <NUM> for reception of the post <NUM> of the anvil head <NUM>. The central opening <NUM> is dimensioned to facilitate movement of the backup member <NUM> about the post <NUM> from a pre-fired, retracted or first position to a post-fired, advanced or second position within the recess <NUM> of the anvil head <NUM>. The backup member <NUM> is retained in the proximal position by the inner race <NUM> of the anvil head <NUM>, which supports the ring cup <NUM> in the proximal position (<FIG>), as will be described.

The backup member <NUM> includes a pair of diametrically opposed fingers <NUM> extending inwardly into the central opening <NUM>. The fingers <NUM> are engaged by the anvil center rod to prevent the backup member <NUM> from moving in a proximal direction and to maintain the anvil head <NUM> in the operative condition (e.g., untilted). Pivotal movement of the anvil head <NUM> relative to the anvil center rod is permitted only after the fingers <NUM> are distally spaced from the anvil center rod.

The backup member <NUM> of the ring assembly <NUM> further includes an annular wall or ring <NUM>, and a disc-shaped platform <NUM> extending radially outward from a distal portion of the annular wall <NUM>. The annular wall <NUM> has a lip <NUM> extending radially inward from a proximal portion thereof. The lip <NUM> is configured to engage (e.g., via snap-fit engagement) the ring cup <NUM> to retain the ring cup <NUM> with the backup member <NUM>. The backup member <NUM> may be formed from a hard material such as metal, although other materials of construction are envisioned.

The ring cup <NUM> of the ring assembly <NUM> supports the cut ring <NUM> therein and guides the annular knife <NUM> into the cut ring <NUM> to prevent partial or offset cutting of the cut ring <NUM>. The ring cup <NUM> is nested with the backup member <NUM> by being captured between an inner peripheral surface <NUM> of the anvil head <NUM> and the backup member <NUM>. The ring cup <NUM> generally includes an annular outer wall <NUM>, an annular, first inner wall <NUM>, and a disc-shaped base <NUM> interconnecting the outer wall <NUM> and the first inner wall <NUM>. The outer wall <NUM>, the base <NUM>, and the first inner wall <NUM> cooperatively define a cavity or annular chamber <NUM> dimensioned for receipt of the cut ring <NUM>.

As best shown in <FIG>, the outer wall <NUM> of the ring cup <NUM> has an annular, outer peripheral surface 360a and an annular, inner peripheral surface 360b, wherein a thickness of the annular wall <NUM> is defined therebetween. An outer lip <NUM> extends radially outward from the outer peripheral surface 360a of the outer wall <NUM>. The outer lip <NUM> of the outer wall <NUM> overlaps the inner race <NUM> of the anvil head <NUM> to support the ring assembly <NUM> in the proximal position and resist movement of the ring assembly <NUM> toward the distal position.

The outer wall <NUM> may have a plurality of slits <NUM> defined therein. The slits are arranged circumferentially about the outer wall <NUM>. The slits <NUM> render the outer wall <NUM> flexible, such that upon distal advancement of the ring assembly <NUM> through the recess <NUM> of the anvil head <NUM>, the outer wall <NUM> may flex or bend radially inward to snap into place under the inner race <NUM> of the anvil head <NUM>. In embodiments, instead of or in addition to having the slits <NUM>, the outer wall <NUM> may be fabricated from a flexible material to facilitate radial contraction of the outer wall <NUM> during assembly into the anvil head <NUM>.

The outer wall <NUM> of the ring cup <NUM> further includes a chamfered surface <NUM> that slopes downwardly (e.g., distally) from a proximal-most surface of the outer wall <NUM>. An annular inner edge <NUM> of the chamfered surface <NUM> (<FIG>) is disposed radially inward of the inner peripheral surface 360b of the outer wall <NUM>, such that the chamfered surface <NUM> defines an undercut or overhang <NUM>. The undercut <NUM> overlays an outer edge <NUM> of the cut ring <NUM> to capture the cut ring <NUM> in the annular chamber <NUM> of the ring cup <NUM>. As such, as the annular knife <NUM> advances, the chamfered surface <NUM> guides or redirects the knife <NUM> inwardly and into contact with the cut ring <NUM> at a location radially inward of the outer edge <NUM> of the cut ring <NUM>. This eliminates the possibility of a line-to-line stapling condition.

It is contemplated that the location at which the knife <NUM> contacts the cut ring <NUM> may be adjusted by adjusting the depth of the undercut <NUM>. For example, to ensure that the knife <NUM> contacts the cut ring <NUM> at a more radially inward location, the depth of the undercut <NUM> in the outer wall <NUM> may be increased. In addition or in the alternative to increasing the depth of the undercut <NUM>, the annular inner edge <NUM> of the chamfered surface <NUM> may extend a greater distance radially inward relative to the inner peripheral surface 360b of the outer wall <NUM> to cause the knife <NUM> to contact the cut ring <NUM> at a more radially inward location.

The ring cup <NUM> further includes an annular, second inner wall <NUM> disposed radially inward of the first inner wall <NUM>. The second inner wall <NUM> may be coupled to the first inner wall <NUM> via a plurality of bridge members <NUM> that permit the second inner wall <NUM> to flex relative to the first inner wall <NUM>. The second inner wall <NUM> may also include a plurality of slits <NUM> defined therein. The slits <NUM> are arranged circumferentially about the second inner wall <NUM> to further facilitate flexing of the second inner wall <NUM>. To assemble the ring cup <NUM> to the backup member <NUM>, the second inner wall <NUM> of the ring cup <NUM> is flexed radially inward and captured under the lip <NUM> of the backup member <NUM>.

The cut ring <NUM> of the ring assembly <NUM> is received in the annular chamber <NUM> of the ring cup <NUM> between the outer wall <NUM> of the ring cup <NUM> and the first inner wall <NUM> of the ring cup <NUM>. The outer edge <NUM> of the cut ring <NUM> is disposed under the undercut <NUM> of the chamfered surface <NUM> of the ring cup <NUM>. It is contemplated that the cut ring <NUM> may be press fit onto the ring cup <NUM>. Thus, movement of the ring cup <NUM> between proximal and distal positions causes corresponding movement of the cut ring <NUM>. In embodiments, the cut ring <NUM> may be formed through a molding process, e.g., an injection molding process, and extend through a plurality of holes <NUM> (<FIG>) defined through the base portion <NUM> of the ring cup <NUM>.

The cut ring <NUM> may be fabricated from a material having a durometer which permits the annular knife <NUM> to pierce through the cut ring <NUM> and bottom out against the base portion <NUM> of the ring cup <NUM>. As such, all of the ring cup <NUM> or select portions thereof (e.g., the chamfered surface <NUM> and the base portion <NUM>) is fabricated from a harder material than the cut ring <NUM>. Suitable materials for the cut ring <NUM> include polytetrafluoroethylene, polypropylene or polyester. Other materials are contemplated.

In operation, prior to firing a circular stapling instrument having the surgical anvil assembly <NUM> of the presently described embodiment, the ring assembly <NUM> including the backup member <NUM>, the ring cup <NUM>, and the cut ring <NUM>, is in its retracted or proximal position, as shown in <FIG>. The outer lip <NUM> of the outer wall <NUM> of the ring cup <NUM> overlaps the inner race <NUM> of the anvil head <NUM> to support the ring assembly <NUM> in the proximal position. With the ring assembly <NUM> in the proximal position, the inwardly extending fingers <NUM> of the backup member <NUM> are engaged by the anvil center rod to maintain the anvil head <NUM> in the first, operative condition, as described above.

Upon actuation of the stapling instrument, the annular knife <NUM> is advanced into engagement with the cut ring <NUM> of the ring assembly <NUM>. In some instances, a section of the annular knife <NUM> may be out of vertical registration with the cut ring <NUM> (e.g., disposed radially outward). In these instances, as the knife <NUM> is advanced, the knife <NUM> engages the chamfered surface <NUM> of the ring cup <NUM>, which directs the knife <NUM> radially inward into vertical registration with the cut ring <NUM>. Due to the chamfered surface <NUM> of the ring cup <NUM> hanging over the cut ring <NUM>, the knife <NUM> makes contact with the cut ring <NUM> radially inward of the outer edge <NUM> of the cut ring <NUM>.

As advancement of the knife <NUM> is continued, the knife <NUM> pierces the cut ring <NUM> and ultimately engages the base portion <NUM> of the ring cup <NUM>, as shown in <FIG>. The force applied by the knife <NUM> flexes or bends the outer wall <NUM> of the ring cup <NUM> inwardly to pass over the inner race <NUM> of the anvil head <NUM>. The ring cup <NUM>, along with the cut ring <NUM> and the backup member <NUM>, is then driven distally toward the distal position.

As the ring assembly <NUM> is advanced toward the distal position, the inwardly extending fingers <NUM> of the backup member <NUM> disengage the anvil center rod, allowing for the anvil head <NUM> to pivot relative to the anvil center rod. It is contemplated that the anvil head <NUM> may be configured to pivot automatically relative to the anvil center rod in any manner described herein. In embodiments, the anvil head <NUM> may be pivoted via any suitable pivoting mechanism, whether it is automatic or manual.

With reference to <FIG>, another embodiment of a surgical anvil assembly <NUM> is illustrated, similar to the anvil assemblies described above. Due to the similarities between the anvil assembly <NUM> of the present embodiment and the anvil assemblies described above, only those elements of the anvil assembly <NUM> deemed necessary to elucidate the differences from anvil assemblies described above will be described in detail.

The anvil assembly <NUM> generally includes an anvil center rod (not shown), similar to the anvil center rods described above, an anvil head <NUM> pivotally mounted to the anvil center rod, and a ring assembly <NUM> configured to selectively unlock the anvil head <NUM> from the anvil center rod. The anvil head <NUM> is configured to pivot relative to the anvil center rod between a first operative condition and a second pivoted or tilted condition. The anvil head <NUM> defines a recess <NUM> therein for receipt of the ring assembly <NUM>. The anvil head <NUM> includes an annular, inner peripheral surface <NUM> that partially defines the recess <NUM>.

The anvil head <NUM> may include a frangible retainer member (not shown), similar to the retainer member <NUM> described in <CIT>. The frangible retainer member may be disposed in the recess <NUM> of the anvil head <NUM> between the inner peripheral surface <NUM> of the anvil head <NUM> and the ring assembly <NUM> so that upon application of a threshold distal force on the ring assembly <NUM>, the frangible retainer collapses, allowing distal advancement of the ring assembly <NUM> and the annular knife <NUM>.

The ring assembly <NUM> is received within the recess <NUM> defined in the anvil head <NUM> and generally includes a backup member <NUM>, a first cut ring <NUM> nested in the backup member <NUM>, and a second cut ring <NUM> nested in the first cut ring <NUM>. The ring assembly <NUM> is moved within the recess <NUM> of the anvil head <NUM> upon application of a force thereto, e.g., during advancement of the annular knife <NUM>.

The backup member <NUM> defines a central opening <NUM> for reception of a post <NUM> of the anvil head <NUM>. The central opening <NUM> is dimensioned to facilitate movement of the backup member <NUM> about the post <NUM> from a pre-fired, retracted or first position to a post-fired, advanced or second position within the recess <NUM> of the anvil head <NUM>. The backup member <NUM>, similar to the backup members described above, includes a pair of diametrically opposed fingers (not explicitly shown) extending inwardly into the central opening <NUM>. The fingers are engaged by the anvil center rod to prevent the backup member <NUM> from moving in a proximal direction and to maintain the anvil head <NUM> in the operative condition (e.g., untilted). Pivotal movement of the anvil head <NUM> relative to the anvil center rod is permitted only after the fingers of the backup member <NUM> are distally spaced from the anvil center rod, as already described above.

The backup member <NUM> further includes an annular wall or ring <NUM> and a disc-shaped platform <NUM> extending radially outward from a distal portion of the annular wall <NUM>. The annular wall <NUM> has a lip <NUM> extending radially inward from a proximal portion thereof. The lip <NUM> is configured to engage (e.g., via snap-fit engagement) the first cut ring <NUM> to retain the first cut ring <NUM> with the backup member <NUM>. The backup member <NUM> may be formed from a hard material such as metal, although other materials of construction are envisioned.

The first cut ring <NUM> of the ring assembly <NUM> supports the second cut ring <NUM> therein and provides a surface on which staples are to be cut. The first cut ring <NUM> is fabricated from a first material, such as, for example, a hard plastic, that resists being pierced by the annular knife <NUM>. The first cut ring <NUM> is nested with the backup member <NUM> by being captured between the inner peripheral surface <NUM> of the anvil head <NUM> and the backup member <NUM>. The first cut ring <NUM> includes a proximal portion 452a, a distal portion 452b, and an annular cutout or recess 452c disposed therebetween. The annular recess 452c is defined in an outer peripheral surface <NUM> of the first cut ring <NUM> and captures the second cut ring <NUM> therein.

The first cut ring <NUM> further defines an annular groove <NUM> in the proximal portion 452a thereof that extends circumferentially along a proximal surface <NUM> of the first cut ring <NUM>. While the groove <NUM> is illustrated as having a V-shaped configuration, it is contemplated that the groove <NUM> may assume any suitable configuration, such as, for example, U-shaped or squared. The groove <NUM> is in vertical registration with the annular recess 452c of the first cut ring <NUM> and is configured to guide the annular knife <NUM> (<FIG>) radially inward toward an apex <NUM> of the groove <NUM>.

The proximal portion 452a of the first cut ring <NUM> has a reduced thickness defined between the apex <NUM> of the groove <NUM> and the annular recess 452c. As such, when the annular knife <NUM> is advanced distally into the proximal portion 452a of the first cut ring <NUM>, the annular knife <NUM> cuts through the proximal portion 452a of the first cut ring <NUM> along a vertical pathway "P" running through the groove <NUM> of the first cut ring <NUM>. The depth of the groove <NUM> may be increased to increase the force necessary for the annular knife <NUM> to cut therethrough, or decreased to decrease the force necessary for the annular knife <NUM> to cut therethrough.

The second cut ring <NUM> of the ring assembly <NUM> is received in the annular recess 452c of the first cut ring <NUM>. As mentioned above, the second cut ring <NUM> is in vertical registration with the groove <NUM> of the first cut ring <NUM>, such that the groove <NUM> of the first cut ring <NUM> guides the annular knife <NUM> into the second cut ring <NUM> at a location radially inward of an outer peripheral surface of the second cut ring <NUM>. It is contemplated that the second cut ring <NUM> may be press fit into the annular recess 452c of the first cut ring <NUM>. Thus, movement of the first cut ring <NUM> between proximal and distal positions causes corresponding movement of the second cut ring <NUM>. The relatively harder first cut ring <NUM> provides a surface on which the annular knife <NUM> can cut through staples without being dragged into the relatively softer second cut ring <NUM>, which is used to cut tissue cleanly.

In embodiments, the second cut ring <NUM> may be formed through a molding process, e.g., an injection molding process. The second cut ring <NUM> may be fabricated from a material having a durometer which permits the annular knife <NUM> to pierce through the second cut ring <NUM> and bottom out against the distal portion 452b of the first cut ring 452b. As such, the second cut ring <NUM> is fabricated from a softer material than the first cut ring <NUM>. Suitable materials for the second cut ring <NUM> include polytetrafluoroethylene, polypropylene or polyester. Other materials are contemplated.

In operation, prior to firing a circular stapling instrument having the surgical anvil assembly <NUM> of the presently described embodiment, the ring assembly <NUM>, including the backup member <NUM>, the first cut ring <NUM>, and the second cut ring <NUM>, is in its retracted or proximal position. The frangible retainer member (not explicitly shown) is interposed between the backup member <NUM> and the inner surface <NUM> of the anvil head <NUM> to support the ring assembly <NUM> in the proximal position. With the ring assembly <NUM> in the proximal position, the inwardly extending fingers of the backup member <NUM> are engaged by the anvil center rod, such that the anvil head <NUM> is retained in the first, operative condition.

Upon actuation of the stapling instrument, the annular knife <NUM> is advanced into engagement with ramped surfaces 462a, 462b (<FIG>) that define the groove <NUM> of the first cut ring <NUM>. The ramped surfaces 462a, 462b direct the knife <NUM> radially inward into vertical registration with a central portion of the second cut ring <NUM>. The annular knife <NUM> moves through the groove <NUM> and contacts the apex <NUM> of the groove <NUM>, transferring the distally-oriented force to the frangible retainer member. Upon applying a threshold force on the frangible retainer member, the frangible retainer member collapses, allowing for distal movement of the ring assembly <NUM> through the recess <NUM> of the anvil head <NUM>.

As the ring assembly <NUM> is advanced toward the distal position, the inwardly extending fingers of the backup member <NUM> disengage from the anvil center rod, allowing for the anvil head <NUM> to pivot relative to the anvil center rod. It is contemplated that the anvil head <NUM> may be configured to pivot automatically relative to the anvil center rod in any manner described herein. In embodiments, the anvil head <NUM> may be pivoted via any suitable pivoting mechanism, whether it is automatic or manual.

As advancement of the annular knife <NUM> is continued, the annular knife <NUM> cuts through the proximal portion 452a of the first cut ring <NUM>, slicing through any tissue and staples along its pathway and dissevering an outer circumferential section of the proximal portion 452a of the first cut ring <NUM> from the remainder of the proximal portion 452a of the first cut ring <NUM>. It is contemplated that the outer circumferential section of the first cut ring <NUM> remains adhered, via friction, to an outer surface of the annular knife <NUM>. As advancement of the annular knife <NUM> is continued, the annular knife <NUM> cuts through the second cut ring <NUM> and ultimately bottoms out on the distal portion 452b of the first cut ring <NUM>. In embodiments, the frangible retainer member may be configured to collapse after the annular knife <NUM> cuts through the proximal portion 452a of the first cut ring <NUM> rather than before.

With reference to <FIG>, another embodiment of a surgical anvil assembly <NUM> is illustrated, similar to the anvil assemblies described above. Due to the similarities between the anvil assembly <NUM> of the present embodiment and the anvil assemblies described above, only those elements of the anvil assembly <NUM> deemed necessary to elucidate the differences from the above anvil assemblies will be described in detail.

With reference to <FIG> and <FIG>, the anvil assembly <NUM> generally includes an anvil center rod (not shown), similar to the anvil center rods described above, an anvil head <NUM> pivotally mounted to the anvil center rod, and a ring assembly <NUM> configured to selectively unlock the anvil head <NUM> from the anvil center rod. The anvil head <NUM> is configured to pivot relative to the anvil center rod between a first operative condition and a second pivoted or tilted condition.

The anvil head <NUM> defines a recess <NUM> therein dimensioned for receipt of the ring assembly <NUM>. The anvil head <NUM> includes a post <NUM> centrally located within the recess <NUM> and projects proximally from a floor of the recess <NUM>. The post <NUM> pivotally couples the anvil head <NUM> to the anvil center rod. For example, the post <NUM> of the anvil head <NUM> may be pivotally coupled to a pair of distal spaced arms of the anvil center rod. The post <NUM> has a body <NUM> having an annular ledge <NUM> projecting radially outward therefrom. The annular ledge <NUM> is configured to selectively maintain the ring assembly <NUM> in a pre-fired, proximal position. The body <NUM> of the post <NUM> defines an annular depression <NUM> disposed underneath or distally of the annular ledge <NUM>.

The ring assembly <NUM> is received within the recess <NUM> defined in the anvil head <NUM> and generally includes a snap collar <NUM> engaged to the body <NUM> of the post <NUM>, a backup member <NUM> supported on the snap collar <NUM>, and a cut ring <NUM> captured between the snap collar <NUM> and the backup member <NUM>. The ring assembly <NUM> is moved within the recess <NUM> upon application of a force thereto, e.g., during advancement of an annular knife, such as, for example, annular knife <NUM> (<FIG> and <FIG>).

With specific reference to <FIG>, the snap collar <NUM> of the ring assembly <NUM> is configured to selectively maintain the ring assembly <NUM> in the proximal position, but allow for movement of the ring assembly <NUM> toward the distal position upon the application of a distally-oriented threshold force thereon. The snap collar <NUM> may be a monolithically formed piece of plastic or may be constructed from a plurality of connected components. The snap collar <NUM> includes a plurality of horizontally-extending support surfaces or flanges <NUM>, and a plurality of vertical extensions <NUM> interposed between respective adjacent pairs of the flanges <NUM>. As such, the flanges <NUM> and vertical extensions <NUM> are alternately arranged around the circumference of the snap collar <NUM>. The snap collar <NUM> may include four flanges <NUM> arranged circumferentially about the snap collar <NUM> in <NUM>° spaced relation to one another. Similarly, the snap collar <NUM> may include four vertical extensions <NUM> arranged circumferentially about the snap collar <NUM> in <NUM>° spaced relation to one another. It is contemplated that the snap collar <NUM> may have more or less than four flanges <NUM> and vertical extensions <NUM>.

The flanges <NUM> of the snap collar <NUM> may be planar and support the backup member <NUM> thereon (<FIG>), such that distal movement of the backup member <NUM> causes distal movement of the snap collar <NUM>. The vertical extensions <NUM> of the snap collar <NUM> may extend proximally, at a perpendicular angle, relative to the flanges <NUM>. The vertical extensions <NUM> each include an annular inner lip <NUM> extending radially inward therefrom, and an annular outer lip <NUM> extending radially outward therefrom. The annular inner lips <NUM> are supported on the annular ledge <NUM> of the post <NUM> of the anvil head <NUM> when the ring assembly <NUM> is in the proximal position. The annular inner lips <NUM> of the snap collar <NUM> resist movement of the ring assembly <NUM> toward the distal position until the distally-oriented threshold force causes outward flexure of the vertical extensions <NUM>, which disengages the annular inner lips <NUM> of the snap collar <NUM> from the annular ledge <NUM> of the post <NUM> of the anvil head <NUM>. The annular outer lips <NUM> of the snap collar <NUM> overlay a proximal surface of the cut ring <NUM> to prevent the cut ring <NUM> from moving relative to the snap collar <NUM>.

With reference to <FIG>, <FIG>, the backup member <NUM> includes a ring body <NUM> defining a central opening <NUM>, a pair of diametrically opposed tabs <NUM> extending radially inward from the annular body <NUM> into the central opening <NUM>, and a pair of diametrically opposed fingers <NUM> extending inwardly into the central opening <NUM>. The central opening <NUM> receives the post <NUM> of the anvil head <NUM> and is dimensioned to facilitate movement of the backup member <NUM> about the post <NUM> from a pre-fired, retracted or first position to a post-fired, advanced or second position within the recess <NUM> of the anvil head <NUM>. The backup member <NUM> is retained in the proximal position via the snap collar's <NUM> engagement with the annular ledge <NUM> of the post <NUM>.

The tabs <NUM> of the backup member <NUM> are supported on a first pair of diametrically opposed flanges <NUM> of the snap collar <NUM>. The tabs <NUM> of the backup member <NUM> are configured to transfer a distally-oriented force, applied by an advancement of the annular knife <NUM>, to the snap collar <NUM>. The fingers <NUM> of the backup member <NUM> extend radially inward from the ring body <NUM> a further extent than do the tabs <NUM> of the backup member <NUM> and are received in cutouts <NUM> in the body <NUM> of the post <NUM>. The fingers <NUM> of the backup member <NUM> have a first portion 598a extending horizontally from the ring body <NUM> of the backup member <NUM>, and a second portion 598b extending vertically upward or proximal from the first portion 598a. The first portion 598a of each of the fingers <NUM> is supported on a second pair of diametrically opposed flanges <NUM> of the snap collar <NUM>.

The second portion 598b of the fingers <NUM> are engaged by the anvil center rod to prevent the backup member <NUM> from moving in a proximal direction and to maintain the anvil head <NUM> in the operative condition (e.g., untilted). Pivotal movement of the anvil head <NUM> relative to the anvil center rod is permitted only after the fingers <NUM> of the backup member <NUM> are distally spaced from the anvil center rod. The backup member <NUM> may be stamped from a hard material such as metal, although other materials of construction are envisioned.

With reference to <FIG>, <FIG>, <FIG>, <FIG>, the cut ring <NUM> of the ring assembly <NUM> is supported on the backup member <NUM> and has an inner peripheral surface <NUM> that is captured between the annular outer lip <NUM> of the snap collar <NUM> and the tabs <NUM> and fingers <NUM> of the backup member <NUM>. Accordingly, proximal or distal movement of the backup member <NUM> results in a corresponding proximal or distal movement of the snap collar <NUM> and the cut ring <NUM>. The cut ring <NUM> has a plurality of surface features <NUM> protruding from an outer peripheral surface thereof. The surface features <NUM> are press fit under an inner race <NUM> of the anvil head <NUM> to retain the ring assembly <NUM> in the recess <NUM>.

The cut ring <NUM> may be fabricated from a material having a durometer which permits the annular knife <NUM> to pierce through the cut ring <NUM> and bottom out against the ring body <NUM> of the backup member <NUM>. As such, the backup member <NUM> may be fabricated from a harder material than the cut ring <NUM>. Suitable materials for the cut ring <NUM> include polytetrafluoroethylene, polypropylene or polyester. Other materials are contemplated.

In operation, prior to firing of a circular stapling instrument having the surgical anvil assembly <NUM> of the presently described embodiment, the ring assembly <NUM>, including the backup member <NUM>, the snap collar <NUM>, and the cut ring <NUM>, is in its retracted or proximal position in the recess <NUM> of the anvil head <NUM>, as shown in <FIG>. The annular inner lips <NUM> of the snap collar <NUM> are supported on the annular ledge <NUM> of the post <NUM> of the anvil head <NUM>, and the surface features <NUM> of the cut ring <NUM> are supported on the inner race <NUM> of the anvil head <NUM>. With the ring assembly <NUM> in the proximal position, the inwardly extending fingers <NUM> of the backup member <NUM> are engaged by the anvil center rod, such that the anvil head <NUM> is retained in the first, operative condition.

Upon actuation of the stapling instrument, the annular knife is advanced into engagement with the cut ring <NUM> of the ring assembly <NUM>, which transfers the distally-oriented force to the backup member <NUM>, which in turn transfers the distally-oriented force to the snap collar <NUM>. Upon achieving a threshold force, the vertical extensions <NUM> of the snap collar <NUM> flex outwardly to separate the annular inner lips <NUM> of the snap collar <NUM> from the annular ledge <NUM> of the post <NUM> of the anvil head <NUM>.

With the annular inner lips <NUM> of the snap collar <NUM> out of overlapping engagement with the annular ledge <NUM> of the post <NUM> of the anvil head <NUM>, the distally-oriented force imparted by the annular knife drives the ring assembly <NUM> distally, whereby the backup member <NUM> contacts the inner surface <NUM> of the anvil head <NUM>, and the annular inner lips <NUM> of the snap ring <NUM> are received in the depression <NUM> of the post <NUM> of the anvil head <NUM>, as shown in <FIG>. Continued advancement of the annular knife causes the annular knife to pierce the cut ring <NUM> and ultimately bottom out against the ring body <NUM> of the backup member <NUM>.

In embodiments, the cut ring <NUM> and the snap collar <NUM> may be configured such that the annular knife cuts through the cut ring <NUM> prior to moving the snap collar <NUM> out of engagement with the annular ledge <NUM> of the post <NUM> of the anvil head <NUM>.

As the ring assembly <NUM> is advanced toward the distal position, the inwardly extending fingers <NUM> of the backup member <NUM> disengage from the arms of the anvil center rod, allowing for the anvil head <NUM> to pivot relative to the anvil center rod. It is contemplated that the anvil head <NUM> may be configured to pivot automatically relative to the anvil center rod in any manner described herein. In embodiments, the anvil head <NUM> may be pivoted via any suitable pivoting mechanism, whether it is automatic or manual.

The anvil assembly <NUM> includes an anvil center rod <NUM> and an anvil head <NUM> pivotally mounted to the anvil center rod <NUM>. The anvil head <NUM> is adapted to pivot between a first operative condition depicted in <FIG> and a second pivoted or tilted condition depicted in <FIG>. The anvil head <NUM> includes a housing <NUM> having a post <NUM> and an anvil tissue contact surface <NUM>. The post <NUM> may include a pair of spaced post arms defining transverse bores <NUM> extending through the spaced post arms. The anvil center rod <NUM> is at least partially positioned about the post <NUM> and coupled to the anvil head <NUM> through a pivot member <NUM>.

The anvil center rod <NUM> may include a pair of distal spaced arms <NUM> defining a pair of diametrically opposed, longitudinally-extending slots <NUM>. The distal spaced arms <NUM> includes a distal end through which transverse bores <NUM> are defined for receiving the pivot member <NUM> that pivotally couples the post <NUM> of the anvil head <NUM> to the distal spaced arms <NUM> of the anvil center rod <NUM>. The pivot member <NUM> is coupled to a first location "L1" of the post <NUM> of the anvil head <NUM> and which is aligned with a central longitudinal axis "X" defined by the anvil center rod <NUM>.

The anvil assembly <NUM> further includes a pivoting assembly <NUM>, which replaces the conventional plunger and cam latch assembly for driving the tilting of the anvil head <NUM>. The pivoting assembly <NUM> is at least partially received within the anvil center rod <NUM>, e.g., between the spaced arms <NUM>, and is spring biased in a proximal direction by a biasing member <NUM>, such as, for example, a coil spring. The pivoting assembly <NUM> includes a linkage arm <NUM> received in one of the slots <NUM> of the distal spaced arms <NUM> of the anvil center rod <NUM>. The linkage arm <NUM> has an L-shaped configuration and includes an elongated shaft <NUM> and a foot or flange <NUM> extending perpendicularly from a proximal end 606a of the shaft <NUM>. In embodiments, the linkage arm <NUM> may assume any suitable shape, such as, for example, linear, curved, or the like. The foot <NUM> of the linkage arm <NUM> has a detent or post <NUM> extending distally therefrom for supporting the biasing member <NUM> of the pivoting assembly <NUM>.

The shaft <NUM> of the linkage arm <NUM> is disposed off-center from the central longitudinal axis "X" of the anvil center rod <NUM>. The shaft <NUM> has a distal end 606b pivotally coupled to a second location "L2" of the post <NUM> of the anvil head <NUM> via a pivot member <NUM>, such as, for example, a pin. The second location "L2" of the post <NUM> of the anvil head <NUM> at which the shaft <NUM> is pivotally coupled is both distal and laterally offset from the first location "L1" at which the anvil center rod <NUM> is pivotally coupled to the post <NUM> of the anvil head <NUM>. As such, a longitudinal translation of the shaft <NUM> in the proximal or distal direction effects a pivoting of the anvil head <NUM> about the first location "L1" in a counter-clockwise or clockwise direction, respectively.

The biasing member <NUM> of the pivoting assembly <NUM> is disposed within the anvil center rod <NUM> and in alignment with the central longitudinal axis "X" of the anvil center rod <NUM> and the first location "L1. " The biasing member <NUM> defines a bore <NUM> therethrough that receives the detent <NUM> of the foot <NUM> of the linkage arm <NUM> to support the biasing member <NUM>. The biasing member <NUM> is interposed between the foot <NUM> of the linkage arm <NUM> and the post <NUM> of the anvil head <NUM> while being in a compressed state. As such, the compressed biasing member <NUM> exerts a proximally-oriented force on the foot <NUM> of the linkage arm <NUM>, which is transferred to the second location "L2" of the post <NUM> of the anvil head <NUM>. Accordingly, upon unlocking the anvil head <NUM> from the anvil center rod <NUM>, the biasing member <NUM> drives or pulls the anvil head <NUM> toward the second, tilted condition, as will be described.

The anvil assembly <NUM> may further include a backup member (not shown) and a cut ring (not shown), similar to the backup members and cut rings described above. The backup member is moved within a recess <NUM> defined in the housing <NUM> of the anvil head <NUM> upon application of a force thereto, e.g., during advancement of an annular knife <NUM> (<FIG> and <FIG>).

In operation, prior to firing of a circular stapling instrument having the surgical anvil assembly <NUM> of the presently described embodiment, the backup member is in its retracted or proximal position in the recess <NUM> of the anvil head <NUM>. With the backup member in the proximal position, the backup member is engaged by the spaced arms <NUM> of the anvil center rod <NUM>, such that the anvil head <NUM> is retained in the first, operative condition and prevented from pivoting despite the proximally-oriented force exerted by the biasing member <NUM> on the anvil head <NUM> via the linkage arm <NUM>.

Upon actuation of the stapling instrument, the annular knife is advanced into engagement with the cut ring, which transfers the distally-oriented force to the backup member, as described in previous embodiments. As the backup member is advanced toward the distal position, the backup member disengages from the arms <NUM> of the anvil center rod <NUM>, unlocking the anvil head <NUM> from the anvil center rod <NUM>. With the anvil head <NUM> unlocked from the anvil center rod <NUM>, e.g., the anvil head <NUM> is free to pivot, the biasing member <NUM> of the pivoting assembly <NUM> drives the linkage arm <NUM> in a proximal direction, whereby the linkage arm <NUM> pivots the anvil head <NUM> relative to the anvil center rod <NUM> in the counter-clockwise direction, indicated by arrow "B" in <FIG>. After the anvil head <NUM> pivots to the second, tilted condition, the anvil head <NUM> covers the linkage arm <NUM>, preventing the linkage arm <NUM> from getting caught on tissue during removal of the surgical anvil assembly <NUM> from a surgical site.

During some operations, the anvil head <NUM> may be manually pivoted back to the first, operative condition against the spring bias of the biasing member <NUM>. In such instances, as the anvil head <NUM> is pivoted back to the first, operative condition, the linkage arm <NUM> is driven or pulled in a distal direction and the biasing member <NUM> is compressed between the foot <NUM> of the linkage arm <NUM> and the post <NUM> of the anvil head <NUM>, resetting the pivoting assembly <NUM>.

The anvil assembly <NUM> includes an anvil center rod <NUM> and an anvil head <NUM> pivotally mounted to the anvil center rod <NUM>. The anvil head <NUM> is adapted to pivot between a first, operative condition and a second, pivoted or tilted condition. The anvil center rod <NUM> may include a pair of distal spaced arms <NUM> for capturing a <NUM> post of the anvil head <NUM> therebetween. The distal spaced arms <NUM> of the anvil center rod <NUM> defines transverse bores <NUM> therethrough for receiving a pivot member <NUM>, as will be described.

The anvil head <NUM> includes a housing <NUM> defining a recess <NUM> therein and the post <NUM> is centrally disposed within the recess <NUM> and extends proximally therefrom. The post <NUM> includes a pair of spaced post arms <NUM> defining a slot <NUM> dimensioned to capture a cam latch <NUM> therein. The spaced post arms <NUM> define transverse bores <NUM> therethrough dimensioned for receipt of the pivot member <NUM>. The anvil center rod <NUM> is at least partially positioned about the post <NUM> and coupled to the anvil head <NUM> through the pivot member <NUM> which extends through respective transverse bores <NUM>, <NUM> of the distal spaced arms <NUM> of the anvil center rod <NUM> and the spaced post arms <NUM> of the post <NUM> to pivotally couple the anvil head <NUM> to the anvil center rod <NUM>.

With reference to <FIG> and <FIG>, the cam latch <NUM> is received within the slot <NUM> defined between the spaced post arms <NUM> of the post <NUM> and coupled to the anvil center rod <NUM> and the post <NUM> via the pivot member <NUM>. The cam latch <NUM> defines a bore or pin opening <NUM> through which the pivot member <NUM> extends. The pin opening <NUM> in the cam latch <NUM> is defined by an annular inner surface <NUM> of the cam latch <NUM>. The cam latch <NUM> has a proximally-located edge <NUM> engaged to a plunger <NUM> for driving a rotation of the cam latch <NUM>. The cam latch <NUM> is rotationally fixed within the slot <NUM> of the post <NUM> of the anvil head <NUM>, such that as the cam latch <NUM> rotates, due to a spring bias of the plunger <NUM>, the anvil head <NUM> rotates with the cam latch <NUM> relative to the anvil center rod <NUM>.

As briefly mentioned above, the pivot member <NUM> extends through the transverse bores <NUM> of the distal spaced arms <NUM> of the anvil center rod <NUM>, the transverse bores <NUM> of the spaced post arms <NUM> of the post <NUM>, and the pin opening <NUM> of the cam latch <NUM> to allow for pivoting or rotation of the anvil head <NUM> relative to the anvil center rod <NUM>. The pivot member <NUM> extends through the bores <NUM>, <NUM> and the pin opening <NUM> in a slip fit manner to ease assembly.

The pivot member <NUM> is an elongated pin-like structure having opposing first and second ends 766a, 766b and an intermediate portion 766c disposed therebetween. It is contemplated that the first and second ends 766a, 766b and the intermediate portion 766c of the pivot member <NUM> may be monolithically formed. An annular groove <NUM> is formed in an outer surface <NUM> of the pivot member <NUM>. The annular groove <NUM> is disposed along the intermediate portion 766c of the pivot member <NUM>. Accordingly, the first and second ends 766a, 766b of the pivot member <NUM> have a first diameter, and the intermediate portion 766c of the pivot member <NUM> has a second diameter, less than the first diameter.

The groove <NUM> in the pivot member <NUM> may be cylindrical and extend circumferentially about the intermediate portion 766c of the pivot member <NUM>. As such, the groove <NUM> has stepped portions 784a, 784b on opposite sides thereof to limit lateral movement of the pivot member <NUM> within and relative to the pin opening <NUM> of the cam latch <NUM>. The diameter of the intermediate portion 766c is less than the diameter of the pin opening <NUM> of the cam latch <NUM>. This allows for a simplified slip fit of the pivot member <NUM> into the pin opening <NUM> of the cam latch <NUM> during assembly.

With reference to <FIG>, the inner surface <NUM> of the cam latch <NUM> has a proximal portion <NUM> that is received in the groove <NUM> of the pivot member <NUM> and which is spring biased into contact with the outer surface <NUM> of the pivot member <NUM> via the plunger <NUM>, as will be described. The length of the groove <NUM> is greater than the thickness of the cam latch <NUM> to allow for some lateral movement of the pivot member <NUM> within the pin opening <NUM> of the cam latch <NUM>.

The anvil assembly <NUM> further includes the plunger <NUM> and a plunger spring <NUM>. The plunger <NUM> is at least partially received within the anvil center rod <NUM>, e.g., between the spaced arms <NUM>, and is spring biased in a distal direction by the plunger spring <NUM>. The plunger <NUM> includes a plunger finger <NUM> engaged to the proximal edge <NUM> of the cam latch <NUM> to maintain the proximal portion <NUM> of the inner surface <NUM> of the cam latch <NUM> in the groove <NUM> of the pivot member <NUM>. Due to the spring bias of the plunger <NUM> on the cam latch <NUM>, the proximal portion <NUM> of the inner surface <NUM> of the cam latch <NUM> is frictionally engaged with the outer surface <NUM> of the pivot member <NUM> to retain the pivot member <NUM> in the pin opening <NUM> of the cam latch <NUM>.

The anvil assembly <NUM> further includes a backup member <NUM> and a cut ring <NUM>, similar to the backup members and cut rings described above. The backup member <NUM> is moved within the recess <NUM> of the anvil head <NUM> upon application of a force thereto, e.g., during advancement of an annular knife <NUM> (<FIG> and <FIG>). The backup member <NUM> includes a pair of diametrically opposed fingers (not explicitly shown) extending inwardly. The fingers are engaged by the spaced arms <NUM> of the anvil center rod <NUM> to prevent the backup member <NUM> from moving in a proximal direction and to maintain the anvil head <NUM> in the operative condition (e.g., untilted). Pivotal movement of the anvil head <NUM> relative to the anvil assembly <NUM> is permitted only after the fingers <NUM> are distally spaced from the arms <NUM> of the anvil center rod <NUM>, as described in the previous embodiments.

In operation, prior to firing of a circular stapling instrument having the surgical anvil assembly <NUM> of the presently described embodiment, the backup member <NUM> is in its retracted or proximal position in the <NUM> recess of the anvil head <NUM>. With the backup member <NUM> in the proximal position, the inwardly extending fingers of the backup member <NUM> are engaged by the spaced arms <NUM> of the anvil center rod <NUM>, such that the anvil head <NUM> is retained in the first, operative condition and prevented from pivoting despite the distally-oriented force exerted by the plunger <NUM> on the anvil head <NUM> via the cam latch <NUM>.

Upon actuation of the stapling instrument, the annular knife <NUM> is advanced into engagement with the cut ring <NUM>, which transfers the distally-oriented force to the backup member <NUM>. As the backup member <NUM> is advanced toward the distal position, the inwardly extending fingers of the backup member <NUM> disengage from the arms <NUM> of the anvil center rod <NUM>, unlocking the anvil head <NUM> from the anvil center rod <NUM>. With the anvil head <NUM> unlocked from the anvil center rod <NUM> (e.g., the anvil head <NUM> is free to pivot), the spring biased plunger <NUM> drives a rotation of the cam latch <NUM> about the pivot member <NUM>. Due to the cam latch <NUM> being rotationally fixed within the anvil head <NUM>, the anvil head <NUM> is caused to rotate relative to the anvil center rod <NUM> about the pivot member <NUM>. In embodiments, the pivot member <NUM> may rotate with the anvil head <NUM>.

With reference to <FIG>, another embodiment of a surgical anvil assembly <NUM> is illustrated, similar to the anvil assemblies described above. Due to the similarities between the anvil assembly <NUM> of the present embodiment and the anvil assemblies described above, only those elements of the anvil assembly <NUM> deemed necessary to elucidate the differences from the anvil assemblies above will be described in detail.

The anvil assembly <NUM> includes an anvil center rod <NUM> and an anvil head <NUM> pivotally mounted to the anvil center rod <NUM>. The anvil head <NUM> is adapted to pivot between a first, operative condition and a second, pivoted or tilted condition (<FIG> and <FIG>). The anvil center rod <NUM> may include a pair of distal spaced arms <NUM> for capturing a post <NUM> of the anvil head <NUM> therebetween. The distal spaced arms <NUM> of the anvil center rod <NUM> define transverse bores therethrough for receiving a pivot member <NUM>.

The anvil head <NUM> defines a recess <NUM> therein. The post <NUM> is centrally disposed within the recess <NUM> and extends proximally therefrom. The post <NUM> includes a pair of spaced post arms <NUM> defining a slot <NUM> dimensioned to capture a cam latch <NUM> therein. The spaced post arms <NUM> define transverse bores <NUM> therethrough dimensioned for receipt of the pivot member <NUM>. The anvil center rod <NUM> is at least partially positioned about the post <NUM> and coupled to the anvil head <NUM> through the pivot member <NUM> which extends through respective transverse bores of the distal spaced arms <NUM> of the anvil center rod <NUM> and the spaced post arms <NUM> of the post <NUM> to pivotally couple the anvil head <NUM> to the anvil center rod <NUM>. The post <NUM> further includes a pair of flanges <NUM> projecting proximally from the respective pair of post arms <NUM>. The flanges <NUM> each have a vertical surface <NUM> projecting perpendicularly from a rounded surface <NUM> of the respective post arms <NUM>.

The cam latch <NUM> is received between the spaced post arms <NUM> of the post <NUM> and between the flanges <NUM>. The cam latch <NUM> is coupled to the anvil center rod <NUM> and the post <NUM> via the pivot member <NUM> which extends through a bore or pin opening <NUM> of the cam latch <NUM>. As best shown in <FIG>, the cam latch <NUM> has an outer peripheral surface <NUM> that includes a camming region 852a and a notched region 852b contiguous with the camming region 852a. The camming region 852a may have an arcuate shape and is configured to be engaged with a plunger <NUM> (<FIG>) that drives a rotation of the cam latch <NUM>.

The notched region 852b of the cam latch <NUM> has a profile that matches a profile cooperatively defined by the vertical surface <NUM> of the flanges <NUM> and the rounded surface <NUM> of the spaced post arms <NUM>. The notched region 852b includes a stop surface <NUM> that extends substantially radially inward from an end of the camming region 852b. The stop surface <NUM> is configured to engage a plunger finger <NUM> of the plunger <NUM> upon the anvil head <NUM> entering the second, titled condition, as shown in <FIG> and <FIG>. The cam latch <NUM> is rotationally fixed within the slot <NUM> of the post <NUM> of the anvil head <NUM>, such that as the cam latch <NUM> rotates, due to a spring bias of the plunger <NUM>, the anvil head <NUM> rotates with the cam latch <NUM> relative to the anvil center rod <NUM>.

The anvil assembly <NUM> further includes the plunger <NUM> and a plunger spring <NUM>. The plunger <NUM> is at least partially received within the anvil center rod <NUM>, e.g., between the spaced arms <NUM>, and is spring biased in a distal direction by the plunger spring <NUM>. The plunger spring <NUM> has a spring constant high enough to prevent a manual compression of the plunger spring <NUM>. As such, manual pivoting of the anvil head <NUM> from the tilted condition back towards the untilted condition is resisted by the plunger spring <NUM>.

The plunger <NUM> includes the plunger finger <NUM> at its distal end, which is engaged to the camming region 852a of the cam latch <NUM> to bias the cam latch <NUM> and, in turn, the anvil head <NUM>, toward the second, tilted condition. When the anvil head <NUM> is free to pivot relative to the anvil center rod <NUM>, the plunger finger <NUM> pushes against the camming region 852a of the cam latch <NUM>, whereby the camming region 852a of the cam latch <NUM> rides along the plunger finger <NUM>, rotating the anvil head <NUM>. Upon the anvil head <NUM> entering the second, tilted condition, the notched region 852b of the cam latch <NUM> passes over the plunger finger <NUM>, whereby the stop surface <NUM> of the cam latch <NUM> is positioned in contact with the plunger finger <NUM>. Due to the contact between the stop surface <NUM> of the cam latch <NUM> and the plunger finger <NUM>, rotation of the cam latch <NUM> in the opposite direction (e.g., rotation of the anvil head <NUM> back toward the first, operative condition) is resisted by the plunger <NUM> and the plunger spring <NUM>.

The anvil assembly <NUM> further includes a backup member <NUM> and a cut ring <NUM>, similar to the backup members and cut rings described above. The backup member <NUM> is moved within the recess <NUM> of the anvil head <NUM> upon application of a force thereto, e.g., during advancement of the annular knife <NUM> (<FIG> and <FIG>). The backup member <NUM> includes a pair of diametrically opposed fingers <NUM> extending inwardly. The fingers <NUM> are engaged by the spaced arms <NUM> of the anvil center rod <NUM> to prevent the backup member <NUM> from moving in a proximal direction and to maintain the anvil head <NUM> in the operative condition (e.g., untilted). Pivotal movement of the anvil head <NUM> relative to the anvil assembly <NUM> is permitted only after the fingers <NUM> are distally spaced from the arms <NUM> of the anvil center rod <NUM>.

In operation, prior to firing of a circular stapling instrument having the surgical anvil assembly <NUM> of the presently described embodiment, the backup member <NUM> is in its retracted or proximal position in the recess <NUM> of the anvil head <NUM>. With the backup member <NUM> in the proximal position, the inwardly extending fingers <NUM> of the backup member <NUM> are engaged by the spaced arms <NUM> of the anvil center rod <NUM> such that the anvil head <NUM> is retained in the first, operative condition and prevented from pivoting despite the distally-oriented force exerted by the plunger <NUM> on the anvil head <NUM> via the cam latch <NUM>.

Upon actuation of the stapling instrument, the annular knife <NUM> is advanced into engagement with the cut ring <NUM>, which transfers the distally-oriented force to the backup member <NUM>. As the backup member <NUM> is advanced toward the distal position, the inwardly extending fingers <NUM> of the backup member <NUM> disengage from the arms <NUM> of the anvil center rod <NUM>, unlocking the anvil head <NUM> from the anvil center rod <NUM>, as described in detail above. With the anvil head <NUM> unlocked from the anvil center rod <NUM> (e.g., the anvil head <NUM> is free to pivot), the spring biased plunger <NUM> drives a rotation of the cam latch <NUM>. Due to the cam latch <NUM> being rotationally fixed within the anvil head <NUM>, the anvil head <NUM> is caused to rotate relative to the anvil center rod <NUM>.

Upon the anvil head <NUM> rotating to the second, tilted condition, the plunger <NUM> is received in the notched region 852b of the cam latch <NUM>, whereby the stop surface <NUM> of the notched region 852b of the cam latch <NUM> overlaps with the plunger finger <NUM>. As such, an attempt to rotate the anvil head <NUM> back toward the first, operative condition will be resisted by the distally-oriented force exerted on the notched region 852b of the cam latch <NUM> by the spring biased plunger <NUM>. As noted above, the biasing member <NUM> has a spring constant high enough to resist a manual attempt at resetting the anvil head <NUM>.

The anvil assembly <NUM> generally includes an anvil center rod (not shown), similar to the anvil center rods described above, an anvil head <NUM> pivotally mounted to the anvil center rod, and a ring assembly <NUM> configured to selectively unlock the anvil head <NUM> from the anvil center rod. The anvil head <NUM> is configured to pivot relative to the anvil center rod between a first operative condition and a second pivoted or tilted condition.

The anvil head <NUM> includes an inner surface <NUM> defining a recess <NUM> therein dimensioned for receipt of the ring assembly <NUM>. The inner surface <NUM> has an outer periphery <NUM> that defines an annular groove <NUM> therein. The groove <NUM> extends radially outward from the recess <NUM> and is in communication therewith. The groove <NUM> is disposed adjacent a tissue contacting surface <NUM> of the anvil head <NUM> and extends circumferentially about the outer periphery <NUM> of the inner surface <NUM> of the anvil head <NUM>. A height of the groove <NUM> is defined between a proximal ledge 975a and a distal ledge 975b thereof.

The ring assembly <NUM> includes a backup member <NUM>, similar to backup member <NUM> described above, and a cut ring <NUM>. The backup member <NUM> is received in the recess <NUM> of the anvil head <NUM>, and the cut ring <NUM> is nested in the backup member <NUM>. The cut ring includes an annular inner body portion 978a and an annular outer body portion 978b integrally formed with, and disposed circumferentially about, the inner body portion 978a. The inner and outer body portions 978a, 978b may be formed from a unitary piece of polytetrafluoroethylene, polypropylene or polyester. Other materials are contemplated. In some embodiments, the outer body portion 978b may be a separate piece attached to the inner body portion 978a.

The inner body portion 978a of the cut ring <NUM> is supported on the backup member <NUM> and is disposed in the recess <NUM> of the anvil head <NUM>, and the outer body portion 978b of the cut ring <NUM> is captured between the proximal and distal ledges 975a, 975b of the groove <NUM> of the anvil head <NUM>. The cut ring <NUM> has a greater diameter than the diameter of the recess <NUM> of the anvil head <NUM>, such that the cut ring <NUM> may be press-fit into the recess <NUM> during assembly. Once assembled, the outer body portion 978b of the cut ring <NUM> extends radially beyond the backup member <NUM>. Due to the outer body portion 978b of the cut ring <NUM> overlapping with the proximal and distal ledges 975a, 975b, both proximal and distal movement of the outer body portion 978b of the cut ring <NUM> out of the groove <NUM> is resisted. The outer body portion 978b of the cut ring <NUM> may have a reduced thickness in relation to the inner body portion 978a to allow for some play of the outer body portion 978b of the cut ring <NUM> within the groove <NUM>, as will be described. In embodiments, the height of the inner body portion 978a of the cut ring <NUM> may be substantially similar to or the same as the height of the groove <NUM>.

In operation, prior to firing a circular stapling instrument having the surgical anvil assembly <NUM> of the presently described embodiment, the ring assembly <NUM>, including the backup member <NUM> and the cut ring <NUM>, is in its retracted or proximal position. A frangible retainer member (not explicitly shown) is interposed between the backup member <NUM> and the inner surface <NUM> of the anvil head <NUM> to support the ring assembly <NUM> in the proximal position, as shown in <FIG>. With the ring assembly <NUM> in the proximal position, the backup member <NUM> is engaged by the anvil center rod, such that the anvil head <NUM> is retained in the first, operative condition.

Upon actuation of the stapling instrument, an annular knife, such as, for example, the annular knife <NUM> shown in <FIG>, is advanced into engagement with the cut ring <NUM> and dissevers or shears off the outer body portion 978b of the cut ring <NUM> from the inner body portion 978a of the cut ring <NUM>. Upon cutting through the cut ring <NUM>, the annular knife <NUM> engages the backup member <NUM>, thereby driving the backup member <NUM> toward the distal position.

Due to the inner body portion 978a of the cut ring <NUM> being retained with the backup member <NUM>, the inner body portion 978a moves toward the distal position with the backup member <NUM>. The outer body portion 978b of the cut ring <NUM> is captured between the outer periphery <NUM> of the inner surface <NUM> of the anvil head <NUM> and an outer surface of the annular knife <NUM>. Thus, as shown in <FIG>, the outer body portion 978b of the cut ring <NUM> is held in the groove <NUM> as the inner body portion 978a of the cut ring <NUM> is distally advanced.

As the ring assembly <NUM> is advanced toward the distal position, the backup member <NUM> disengages from the anvil center rod, allowing for the anvil head <NUM> to pivot relative to the anvil center rod. It is contemplated that the anvil head <NUM> may be configured to pivot automatically relative to the anvil center rod in any manner described herein. In embodiments, the anvil head <NUM> may be pivoted via any suitable pivoting mechanism, whether it is automatic or manual.

With reference to <FIG>, a retraction of the annular knife <NUM> back to its starting position causes the outer body portion 978b of the cut ring <NUM> to move proximally within the groove <NUM> due to the frictional engagement between an outer surface of the annular knife <NUM> and an inner peripheral surface <NUM> of the outer body portion 978b of the cut ring <NUM>. The outer body portion 978b of the cut ring <NUM> is dragged proximally by the retracting annular knife <NUM> until the outer body portion 978b of the cut ring <NUM> contacts the proximal ledge 975a. With the outer body portion 978b of the cut ring <NUM> in contact with the proximal ledge 975a, the outer body portion 975b and the inner body portion 978a are axially spaced from one another, creating a passage <NUM> through which staples lodged in the cut ring <NUM> may be removed.

Claim 1:
A circular stapling instrument, comprising:
an anvil assembly (<NUM>) and an annular knife (<NUM>), the anvil assembly comprising
an anvil center rod (<NUM>);
an anvil head (<NUM>) pivotally coupled to the anvil center rod and movable between a first, operative condition and a second, tilted condition, the anvil head including an inner surface (<NUM>) having an outer periphery (<NUM>) to define a recess (<NUM>) therein and a groove (<NUM>) extending radially outward from the recess, the groove having a proximal ledge (975a) and a distal ledge (975b); and
a ring assembly (<NUM>) including:
a backup member (<NUM>) disposed within the recess (<NUM>) of the anvil head; and
a cut ring (<NUM>) nested with the backup member and captured in the groove of the anvil head, wherein the ring assembly is movable within the recess from a proximal position preventing pivotal movement of the anvil head from the first, operative condition, to a distal position permitting pivotal movement of the anvil head to the second, tilted condition, wherein the cut ring includes:
an annular inner body portion (978a) disposed in the recess of the anvil head; and
an annular outer body portion (978b) captured between the proximal and distal ledges of the groove of the anvil head, wherein the outer body portion is configured to be disconnected from the inner body portion upon an advancement of the annular knife (<NUM>) through the cut ring
wherein the inner body portion (978a) of the cut ring is supported on the backup member (<NUM>);
characterised in that a part of the outer body portion (978b) of the cut ring is supported on the backup member (<NUM>) with the outer body portion extending radially beyond the backup member and the outer body portion of the cut ring is configured to be dragged proximally upon a retraction of the annular knife due to frictional engagement between an outer surface of the annular knife (<NUM>) and an inner peripheral surface (<NUM>) of the outer body portion until the outer body portion contacts the proximal ledge (975a), such that the outer body portion and the inner body portion are axially spaced from one another to define a passage (<NUM>).