Abstract:
A storage system for maintaining dimensional tolerances of a plurality of bioabsorbable fasteners from a time of formation to a time of use of the fasteners. The storage system includes a structure defining a cavity. The cavity has a cavity cross-section resembling a corresponding cross-section of the plurality of bioabsorbable fasteners and a cavity length adapted to accept the plurality of the bioabsorbable fasteners in a stacked orientation. The cartridge is fabricated of a material having a heat deflection temperature higher than the temperatures encountered during manufacture, sterilization, shipping or storage. The storage system also includes a locking arrangement operably configured to shield the fasteners from a biasing force outside the cavity until the time of use of the fasteners.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to the field of surgical fasteners such as surgical staples and clips. More particularly, the present invention relates to a mechanical method and apparatus for constraining and protecting bioabsorbable fasteners from outside forces during sterilization, transportation and storage such that fastener tolerances are maintained prior to use.  
       BACKGROUND OF THE INVENTION  
       [0002]     When a wound opening in tissue is created either through an intentional incision or an accidental laceration, biological healing of the wound opening occurs when the opposed living tissue surfaces of the wound opening are in close proximity to each other. If the opening is very large or if its location subjects the wound opening to continual movement, a physician will seek to forcibly hold the sides of the wound opening in close proximity so as to promote the healing process. In the case of skin tissue, for example, healing occurs best when the opposing dermal layers of the skin tissue are held in proximity with each other.  
         [0003]     While traditional suturing remains a popular method of effectuating closure of wound openings, the use of staples and staplers as a closure technique has become increasingly popular, especially in surgical settings where the opening is created through a purposeful incision. In these settings, the incision tends to make a clean, straight cut with the opposing sides of the incision having consistent and non-jagged surfaces.  
         [0004]     Typically, stapling of a skin opening, for example, is accomplished by manually approximating the opposing sides of the skin opening and then positioning the stapler so that a metal staple will span the opening. The stapler is then manipulated such that the staple is driven into the skin with one leg being driven into each side of the skin and the cross-member of the staple extending across the opening external to the skin surface. Generally, the legs of the metal staple are driven into an anvil causing the metal staple to deform so as to retain the skin tissue in a compressed manner within the staple. This process can be repeated along the length of the wound opening such that the entire incision is held closed during the healing process.  
         [0005]     One problem with conventional metal staples is that the metal staples must be removed after the healing process of a wound opening is completed. As the sciences of medical and materials technology have advanced over the course of the past century, new bioabsorbable polymers and copolymers have been developed that provide medical professionals with an alternative to metal staples that must be removed. Fasteners made of bioabsorbable materials, sometimes referred to as bioabsorbable or biodegradable, break down or degrade over time in the body, with the residuals being either absorbed or ultimately expelled by the body&#39;s natural processes.  
         [0006]     While bioabsorbable polymer fasteners are preferable to metal staples because they do not have to be removed, the lack of an effective deformation property of bioabsorbable polymer materials means that these materials cannot rely on the deformation of the staple to compress and retain tissue in a manner similar to a metal staple. For example, after the initial forming steps the bioabsorbable staples and fasteners retain residual stresses that can lead to dimensional variations between similarly formed components if the residual stresses cause the components to relax in an uncontrolled manner. Consequently, different designs for securing bioabsorbable staples have been developed.  
         [0007]     Many bioabsorbable staples utilize a retainer or receiver that performs a self-locking function, either integrated with a piercing portion as shown, for example, in U.S. Pat. No. 4,317,451, or separated to form a two piece staple as shown, for example, in U.S. Pat. Nos. 4,805,617 and 5,902,319. U.S. Pat. No. 4,428,376 describes a bioabsorbable staple with a pivoting arm locking feature that permits the arms of the staple to be inserted in an open position and then locked into a closed position after deployment. Some designs utilize lateral projecting barbs for securing the bioabsorbable staple as shown, for example, in U.S. Pat. Nos. 3,716,058; 3,757,629; 4,014,492; 5,105,252 and 5,584,859. These alternative designs for securing bioabsorbable staples have generally precluded the staples from being stored in a ganged manner similar to metal staples. For example, as shown in U.S. Pat. No. 6,120,526, the need to operate the particular self-locking or retaining function of the bioabsorbable staple can prevent the staples from being loaded into the stapler in a side-by-side ganged fashion like conventional metal staples.  
         [0008]     Another design for a bioabsorbable staple utilizes a single shaft skewer approach as shown for example, in U.S. Pat. Nos. 5,292,326; 5,389,102; 5,489,287; and 5,573,541 issued to Green et al. The Green et al. patents attempted to overcome the need for self-locking or retaining functions of a bioabsorbable stapling system by employing a handheld apparatus with jaws to proximate, interdigitate and overlap opposing sides of dermal layer tissue along the length of a skin opening. The apparatus then drives a single spike through the interdigitated and overlapped dermal layers of the opposing skin surfaces to secure both sides of the dermal tissue on the single spike. By using a single spike passing through interdigitated tissue, the Green et al. patents attempted to overcome the need for self-locking or closure mechanisms as required by other prior art bioabsorbable fasteners. This approach also permitted the spikes described by Green to be stored in a ganged or stacked manner, more like conventional metal staples.  
         [0009]     U.S. Pat. No. 6,726,705 to Peterson et al describes a tissue fastening system that uses bioabsorbable staples that do not need a self-locking or closure mechanism. Unlike the Green et al patents, the Peterson et al. patent utilizes an applicator apparatus for bioabsorbable fasteners that bilaterally drives at least one portion of the fastener through each side of a wound such that the fastener is positioned below an exterior surface of the wound and a portion of the fastener is positioned generally transverse to a vertical interface of the wound. In one embodiment of this patent, an automated fastener delivery and storage mechanism is described in which the bioabsorbable fasteners are stacked vertically in echelon fashion surrounding a guide member. The ganged stack of staples in this embodiment are biased downwardly from a time of manufacture to a time of use using a spring that in use causes the staples in the ganged arrangement to be advanced.  
         [0010]     While the tissue fastening apparatus described in the Peterson et al patent represents a significant improvement over prior art bioabsorbable fasteners, the technique described in the Peterson et al patent for ganging bioabsorbable fasteners uses a constant bias force that may cause the stack of bioabsorbable staples to deform, or stick together when subjected to long periods of time or elevated temperatures prior to use. As such, it would be desirable to provide an improved storage system for bioabsorbable fasteners throughout sterilization, packaging and shipment prior to the time of use.  
       SUMMARY OF THE INVENTION  
       [0011]     The present invention is a system for storing multiple bioabsorbable fasteners in such a manner as to maintain the dimensional tolerances of the bioabsorbable fasteners from a time of formation to a time of use. The system preferably is implemented as a cartridge that comprises a cavity having a cavity cross-section resembling the bioabsorbable fastener and a cavity length for accepting a plurality of the bioabsorbable fasteners in a stacked orientation. The cartridge is fabricated of a material having a heat deflection temperature higher than the temperatures encountered during shipping or storage of the cartridge loaded with fasteners such that relaxation of the bioabsorbable fasteners induced by elevated temperatures during shipment, packaging and assembly processes such as, for example, certain sterilization processes, is constrained by the cartridge. In one embodiment, a locking arrangement is configured as part of the cartridge to shield the fasteners prior to use from a biasing force that is applied at the time of use to eject the fasteners from the cartridge.  
         [0012]     The invention also includes a method for maintaining dimensional tolerances of a bioabsorbable fastener from a time of formation to a time of use. The method comprises loading a cartridge with a plurality of bioabsorbable fasteners in a stacked configuration. The cartridge has an elongated cavity, a first end, a second end, and a cavity cross-section that substantially resembles the bioabsorbable fasteners. The cartridge is fabricated of a material having a heat deflection temperature higher than the temperatures encountered during shipping or storage of the cartridge loaded with the fasteners such that relaxation of the bioabsorbable fasteners induced by elevated temperatures during shipment, packaging and assembly processes such as, for example, certain sterilization processes, is constrained by the cartridge. In one embodiment, the method includes protecting the fasteners from a biasing force that is applied at the time of use to eject the fasteners from the cartridge.  
         [0013]     The invention also includes a medical fastening instrument comprising an instrument body including a biasing member, an insertion member, and a cartridge attached to the instrument body. The cartridge has a continuous cavity adapted to receive a plurality of bioabsorbable fasteners to be stored in stacked relation. The cartridge is fabricated of a material having a heat deflection temperature higher than the temperatures encountered during shipping or storage such that relaxation of the bioabsorbable fasteners induced by elevated temperatures during shipment, packaging and assembly processes such as, for example, certain sterilization processes, is constrained by the cartridge. The biasing member causes the insertion member to interact with the cartridge such that the plurality of bioabsorbable fasteners are selectively ejected from the cartridge. In one embodiment, the instrument also includes a lock for isolating the plurality of fasteners once loaded into the cartridge from the biasing member and the insertion member prior to use of the medical fastening instrument and also from outside forces during shipment and storage of the medical fastening instrument.  
         [0014]     In another embodiment, the invention includes an instrument configured to maintain the dimensional tolerances of a bioabsorbable fastener. The instrument comprises a cartridge having a cavity for receiving a plurality of fasteners. The cavity is defined by a first surface, a second surface opposite the first surface, at least one rear surface joining the first surface and the second surface, and a forward surface opposite the rear surface, the forward surface including a protrusion at the midpoint of the forward surface. The instrument also includes an insertion head coupled to the cartridge and positioned to align the material to be fastened and a lock for isolating the plurality of fasteners from a biasing force that is used to eject the fasteners at a time of use.  
         [0015]     In yet another embodiment, the invention includes a method for maintaining dimensional tolerances of a bioabsorbable fastener. The method includes loading a cartridge with a plurality of bioabsorbable fasteners in a stacked configuration. The cartridge has a cavity for receiving a plurality of fasteners and is defined by a first surface, a second surface opposite the first surface, at least one rear surface joining the first surface and the second surface, and a forward surface opposite the rear surface, the forward surface including a protrusion at the midpoint of the forward surface. The method also includes installing the cartridge within an instrument body. The cartridge and instrument body form an assembled and operable fastening instrument whereby the bioabsorbable fasteners can be selectively discharged. The method also includes protecting the staples from a biasing force used to discharge the fasteners until a time of use with a locking arrangement.  
         [0016]     In a preferred embodiment, the invention includes a medical fastening instrument comprising a body assembly including a biasing member, and a cartridge attached to the body assembly. The cartridge has a cavity for receiving a plurality of fasteners. The cavity includes an entrance and an exit and is defined by a first surface, a second surface opposite the first surface, at least one rear surface joining the first surface and the second surface, and a forward surface opposite the rear surface, the forward surface including a protrusion, at the midpoint of the forward surface. An elongated rod is coupled to the biasing member. The rod is configured to provide a force in the direction of the plurality of fasteners such that the plurality of fasteners are selectively ejected from the exit of the cartridge. A removable lock is configured to prevent movement of the rod until a desired time of use.  
         [0017]     Unlike existing mechanical tissue fastening systems, the present invention recognizes the need for and advantages of a storage system that constrains bioabsorbable fasteners throughout sterilization, packaging and shipment such that critical tolerances are insured at the time of use. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]      FIG. 1  shows a perspective view of a wound closure instrument incorporating the present invention.  
         [0019]      FIG. 2  shows a front view of a wound closure instrument incorporating the present invention.  
         [0020]      FIG. 3  shows an enlarged perspective view of a wound closure instrument incorporating the present invention.  
         [0021]      FIG. 4  shows a partial cross-sectional view of the cartridge of the present invention.  
         [0022]      FIG. 5  shows a top view of the cartridge of the present invention.  
         [0023]      FIG. 6  shows a perspective view of the cartridge of the present invention.  
         [0024]      FIG. 7  shows a rear perspective view of the cartridge of the present invention.  
         [0025]      FIG. 8  an enlarged perspective view of a wound closure instrument incorporating the present invention.  
         [0026]      FIG. 9  is a side view of an instrument incorporating the present invention.  
         [0027]      FIG. 10  is a partial front perspective view of an instrument incorporating the present invention.  
         [0028]      FIG. 11  is a side partial view of an instrument incorporating the present invention.  
         [0029]      FIG. 12  is an enlarged cross-sectional perspective view of an instrument incorporating the present invention.  
         [0030]      FIG. 13  is a partial perspective view of a wound closure instrument incorporating the present invention.  
         [0031]      FIG. 14  is an exploded view of a wound closure instrument incorporating the present invention.  
         [0032]      FIG. 15  is a perspective view of the applicator assembly in accordance with the present invention.  
         [0033]      FIG. 16  is a shows a partial cross-sectional view of an alternative embodiment of the cartridge of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0034]     A wound closure instrument  100  is depicted in  FIGS. 1, 2 , and  3 . For example, wound closure instrument  100  can take the form of the Insorb® Subcuticular Stapler as supplied by Incisive Surgical, Inc. of Plymouth, Minn. and as further described in U.S. Pat. No. 6,726,705 and pending U.S. patent application Ser. Nos. 10/448,838, 10/607,497 and 29/202,831, all of which are incorporated by reference in their entirety. Wound closure instrument  100  is comprised of body assembly  102 , a trigger assembly  104 , a tissue manipulation assembly  106 , an applicator assembly  108 , and a fastener assembly  110 .  
         [0035]     Body assembly  102  preferably comprises a clam shell design with a first molded portion  112   a  and a second molded portion  112   b  that can be snapped together, thermally bonded, adhesively bonded or connected via a plurality of fastening members  114 . Body assembly  102  is preferably fabricated from plastic, although a variety of materials may be used while remaining within the scope of the invention.  
         [0036]     Fastener assembly  110  comprises a plurality of bioabsorbable fasteners  116 , for example the dynamic bioabsorbable fasteners described in U.S. patent application Ser. No. 10/603,397, which is incorporated by reference in its entirety, and a fastener cartridge  200 . Bioabsorbable fasteners  116  are stored within fastener cartridge  200  in a stacked configuration.  
         [0037]     Examples of bioabsorbable materials from which bioabsorbable fasteners  116  can be formed include poly(dl-lactide), poly(l-lactide), polyglycolide, poly(dioxanone), poly(glycolide-co-trimethylene carbonate), poly(l-lactide-co-glycolide), poly(dl-lactide-co-glycolide), poly(l-lactide-co-dl-lactide), poly(caprolactone) and poly(glycolide-co-trimethylene carbonate-co-dioxanone). Other polymer, synthetic or biological materials which are designed for initial structural integrity and have the capability of breaking down over time in the body could also be utilized.  
         [0038]     It has been discovered that, when used in connection with the fastening apparatus of the preferred embodiment, in addition to having the desired property of breaking down over time in the body, these bioabsorbable materials also have a tendency to deform in response to pressures applied over an extended period of time.  
         [0039]      FIG. 4  shows a top cross-sectional view of the fasteners  116  disposed in the cartridge  200 . Cartridge  200  includes a cavity  202  that is defined by a first surface  204 , a second surface  206 , a rear surface  208 , and a forward surface  210 . Forward surface  210  includes a protrusion  212  located at the midpoint of the forward surface  210 . Protrusion  212  is shown extending into cavity  202 , toward rear surface  208 , between first surface  204  and second surface  206 . In one embodiment, forward surface  210  includes kanted portions  222  and  224  extending toward protrusion  212 .  
         [0040]      FIG. 16  shows a top cross-sectional view of a dynamic fastener  116  disposed in a cartridge embodiment  200 . A description of dynamic fasteners is disclosed in U.S. patent application Ser. No. 10/603,397, which is hereby incorporated by reference in its entirety. Cartridge  200  includes a cavity  202  that is defined by a first surface  204 , a second surface  206 , a rear surface  208 , and a forward surface  210 . Forward surface  210  includes a protrusion  212  located at the midpoint of the forward surface  210 . Protrusion  212  is shown extending into cavity  202 , toward rear surface  208 , between first surface  204  and second surface  206 . In one embodiment, forward surface  210  includes kanted portions  222  and  224  extending toward protrusion  212 .  
         [0041]     The dimensions of a preferred embodiment of cavity  202  will now be discussed. Kanted portions  222  and  224  define an angle of between 30 and 90 degrees with respect to one another, preferably between 45 and 75 degrees, more preferably between 55 and 65 degrees. The width of protrusion  212  along the dimension extending into cavity  202  is between 0.010 and 0.042 inches, preferably between 0.018 and 0.034 inches. The width of cavity  202  from first surface  204  to second surface  206  is between 0.130 and 0.150 inches, preferably between 0.138 and 0.142 inches. The maximum height of cavity  202  from kanted portion  222  and rear surface  208  is between 0.190 and 0.210 inches, preferably between 0.197 and 0.203 inches. The distance between the tip of protrusion  212  and rear surface  208  is between 0.090 and 1.110 inches, preferably between 0.092 and 1.108 inches. The rear surface  208  defines a curve with a radius of between 0.060 and 0.080 inches, preferably between 0.065 and 0.075 inches, more preferably 0.070 inches.  
         [0042]     Fasteners  116  include a first tip  214 , a second tip  216 , and a body  218  that joins first tip  214  and second tip  216 . In one embodiment, first tip  214  and second tip  216  include barbs  218  and  220 , respectively.  
         [0043]     In a preferred embodiment, fasteners  116  are constrained within cavity  202  by first surface  204  and second surface  206 . This aspect of the invention is desirable for maintaining a constant distance between the first tip  214  and second tip  216 . Fasteners  116  may also be constrained by any or all of the rear surface  208 , forward surface  210 , kanted portions  222 ,  224  and protrusion  212 .  
         [0044]     During operation and use, downward pressure is preferably applied to the plurality of fasteners  116  by rod  228  and biasing member  230 . Rod  228  includes plug  232  configured to apply pressure to the plurality of fasteners  116  in cavity  202 . Biasing member  230  couples with rod  228  at knob  234 . The pressure generated by biasing member  230  against the interior of body assembly  102  and rod  228  generates a downward force by plug  232  against the plurality of fasteners  116 . It will be recognized that other arrangements for application of a biasing force to the plurality of fasteners  116  could also be utilized whereby the function of the biasing member  230  and rod  228  are combined, such as a spring or a flexible metal member. Alternatively, other structures for applying a biasing force could be used in place of rod  228 , such as piston or a crossbar could be utilized.  
         [0045]     In a preferred embodiment, rod  228  includes a catch  236 . Catch  236  is configured to rest against a corresponding area of molded portion  112  or a removable lock  300 . This enables instrument  100  to be shipped fully assembled to facilitate ease of use by a physician. Preferably, catch  236  and the removable lock  300  prevents biasing member  230  from applying force directly to fasteners  116  during shipment or storage so that the fasteners  116  do not deform after prolonged exposure to the spring force. Preferably, instrument  100  is a multi-shot design in which the plurality of fasteners  116  come preloaded in the cartridge  200  with the cartridge  200  assembled as part of the fastener assembly  110 , thus eliminating any hand loading of individual fasteners. Alternatively, cartridge  200  may be preloaded or hand loaded and designed for insertion into fastener assembly  110  prior to use.  
         [0046]     A preferred embodiment of lock  300  will be described in more detail with respect to  FIGS. 7-13 . Lock  300  includes stopper arms  302 ( a ),  302 ( b ) that extend at approximately a 90 degree angle from lock  300 , through an aperture in instrument  100 . As shown in  FIG. 7 , rod  228  is disposed between stopper  302 ( a ) and  302 ( b ). Rod  228  is positioned at an angle approximately perpendicular to stopper  302 ( a ) and  302 ( b ). Rod  228  includes a wide section  304  near the end of the rod  228  adjacent to the biasing member  230 . Rod  228  also includes a narrow section  306  between the wide section  304  and the plug  232 . As shown in  FIG. 7 , the stopper  302  of lock  300  prevents the wide section  304  of rod  228  from passing through stopper  302 ( a ) and  302 ( b ). In a preferred embodiment, plug  232  is disposed at least partially in the cavity of cartridge  200  when the movement of rod  228  is secured by lock  300 . This mechanism, by its nature, prevents the plurality of fasteners from escaping from the top entrance of the cavity.  
         [0047]     As shown in  FIG. 9 , lock  300  includes lower section  308  that extends into and through insertion head  266  and below cartridge  200 . This feature of the invention holds the plurality of fasteners within the cartridge  200 .  
         [0048]     When instrument  100  is ready to be used, lock  300  is simply pulled away from instrument  100  such that lower section  308  slides out of insertion head  266 . Stopper  302 ( a ),  302 ( b ) move away from rod  228  and enable rod  228  to slide downward due to the pressure of biasing member  230 . The pressure of biasing member  230  enables plug  232  to apply pressure to the plurality of staples  116  so that the lowest staple is positioned against the applicator assembly  108 . In this configuration, instrument  100  is ready for operation. Preferably, the biasing member  230  is a spring member. Alternatively, arrangements of elastic bands or belts, metal flat springs, or even a gas or liquid pressure activated mechanism could be used to provide the desired biasing force.  
         [0049]     Although the present invention has been described with respect to the various embodiments, it will be understood that numerous insubstantial changes in configuration, arrangement or appearance of the elements of the present invention can be made without departing from the intended scope of the present invention. Accordingly, it is intended that the scope of the present invention be determined by the claims as set forth.