Abstract:
A method of forming and deploying an improved absorbable fastener for hernia mesh fixation is disclosed. The absorbable fastener of the present invention functions to securely fasten tough, non macro-porous, and relative inelastic mesh to soft tissue. The fastener is formed from co-polymers of lactide and glycolide.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation Application claiming the benefit of and priority to U.S. patent application Ser. No. 11/161,702, filed on Aug. 12, 2005, which is a Continuation-in-Part Application claiming the benefit of and priority to U.S. patent application Ser. No. 10/907,834, filed on Apr. 18, 2005 (now U.S. Pat. No. 8,114,099), which is a Continuation-in-Part Application claiming the benefit of and priority to U.S. patent application Ser. No. 10/905,020, filed on Dec. 10, 2004 (now abandoned), which is a Continuation-in-Part Application claiming the benefit of and priority to U.S. patent application Ser. No. 10/709,297, filed on Apr. 27, 2004 (now U.S. Pat. No. 7,758,612), the entire contents of each of which is incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to surgical fasteners and their associated applicators, and more particularly, surgically fastening material to tissue and their method of use. 
     In laparoscopic repair of hernia fasteners have been used to attach repair mesh over the hernia defect so that bowel and other abdominal tissue are blocked from forming an external bulge that is typical of abdominal hernias. The role of the fasteners is to keep the mesh in proper position until tissue ingrowth is adequate to hold the mesh in place under various internal and external conditions. Adequate ingrowth usually takes place in 6-8 weeks. After that time the fasteners play no therapeutic role. Fixation fasteners comprise a mesh fixation feature, or head, a mesh-tissue interface section, and a tissue-snaring feature that holds the fastener in place under force developed inside or outside the body. 
     At present, there are a variety of surgical devices and fasteners available for the surgeon to use in endoscopic and open procedures to attach the mesh patch to the inguinal floor or abdominal wall. One such mesh attachment instrument uses a helical wire fastener formed in the shape of a helical compression spring. Multiple helical wire fasteners are stored serially within the 5 mm shaft, and are screwed or rotated into the mesh and the overlaid tissue to form the fastener for the prosthesis. A load spring is used to bias or feed the plurality of helical fasteners distally within the shaft. A protrusion extends into the shaft, while preventing the ejection of the stack of fasteners by the load spring, allows passage of the rotating fastener. U.S. Pat. Nos. 5,582,616 and 5,810,882 by Lee Bolduc, and U.S. Pat. No. 5,830,221 by Jeffrey Stein describe instruments and fasteners of this type. 
     U.S. Pat. Nos. 5,203,864 and 5,290,297 by Phillips describe two embodiments of a hernia fastener and delivery devices. One of the Phillips fasteners is formed in the shape of a unidirectional dart with flexible anchor members. The dart is forced through the mesh and into tissue by a drive rod urged distally by the surgeon&#39;s thumb. The anchor members are forced inward until the distal end of the dart penetrates the overlaid tissue and then the anchor members, presumably, expand outward without any proximal force on the dart thus forming an anchor arrangement. This requires an extremely forceful spring force generated by the anchor members. Multiple darts are stored in a rotating cylinder, much like a revolver handgun. 
     Phillips second fastener embodiment is a flexible H shaped device. The tissue penetrating means is a hollow needle containing one of the legs of the H. The H shape is flattened with the cross member and the other leg remaining outside the hollow needle owing to a longitudinal slot therein. A drive rod urged distally by the surgeon&#39;s thumb again delivers the fastener. The contained leg of the H penetrates the mesh and tissue. After ejection the fastener presumably returns to the equilibrium H shape with one leg below the tissue and one leg in contact with the mesh with the cross member penetrating the mesh and the tissue, similar to some plastic clothing tag attachments. Phillips depicts the installed device returning to the H shape but he fails to teach how to generate enough spring action from the device to overcome the high radial forces generated by the tissue. 
     A series of U.S. Pat. Nos. 6,572,626, 6,551,333, 6,447,524, and 6,425,900 and patent applications 200200877170 and 20020068947 by Kuhns and Kodel, all assigned to Ethicon, describe super elastic, or shape metal fasteners and a delivery mechanism for them. The fasteners are stored in the delivery device in a smaller state and upon insertion into the mesh and tissue, transitions to a larger anchor shaped state. The Ethicon fastener is delivered by an elaborate multistage mechanism through a hollow needle that has penetrated the mesh and the tissue. The hollow needle is then retracted to leave the fastener to change shape to a more suitable configuration for holding the mesh in place. 
     The primary problem associated with metallic fasteners is the formulation of permanent adhesions that attach themselves to the metallic implant. These adhesions can be of such a severity that fistulas are sometimes known to form and fasteners have been reported to migrate into the bowl and bladder. According to joels and others, in Surg Endosc (2005) 19: 780-785, adhesions form on titanium abdominal implants and more severely on shape metal implants. 
     Another major problem with these prior art fasteners is that the mesh is attached to body tissue in as many as 100 places for large ventral hernias. This results in a large quantity of metal remaining in the body as permanent implants, even though after the ingrowth phase the fasteners serve no useful purpose. Compounding this problem the distal ends of the fasteners are sharp pointed and thus pose a continued pain or nerve damage hazard. 
     One alternative to metallic fixation devices is bio-absorbable materials. These materials are degraded in the body by hydrolysis. This precludes permanent pain sites and minimizes or eliminates adhesions since after degradation the body metabolizes them as carbon dioxide and water. These materials require special attention to many design details, however, that is much more demanding than their counterparts in metallic fixation devices such as applicator tool design, sterilization processes, and packaging. Metallic tacks or fasteners provide structural strength that simplifies their insertion and since the materials, usually titanium or nickel-titanium alloys (shape metal), are chemical and radiation resistant and are very temperature tolerant many options are available to the designer that are not available for bio-absorbable materials. 
     The basic considerations of an effective mesh fixation applicator and absorbable fastener are the material strength, absorption time, the sterilization method, and packaging requirements, the ease of insertion of the fastener through the mesh and into the tissue, the ease of ejecting the fastener from the tool, the fixation strength of the fastener once implanted, the time required after insertion for the fastener to be degraded and metabolized by the body are all effected by the choice of fastener material, the geometry of the design, and the forming process. 
     Materials of appropriate strength are generally limited to synthetic materials. Currently, the U.S. FDA has cleared devices made from polyglycolide (PG), polylactide (PL), poly caprolactone, poly dioxanone, trimethylene carbonate, and some of their co-polymers for implant in the human body. These materials and their co-polymers exhibit a wide variation of properties. Flex modulus ranges from a few thousand to a few million PSI, tensile strength ranges from 1000 to 20,000 PSI, in vivo absorption times range from a few days to more than two years, glass transition temperatures range from 30-65 degrees centigrade, all with acceptable bio-responses. Unfortunately, however, the optimum values of each of these properties are not available in any one of these materials so that it is necessary to make performance tradeoffs. 
     Mechanical Properties 
     Most hernia mesh fixation devices are currently used in laparoscopic hernia repair. In general laparoscopic entry ports have been standardized to either 5 or 10 mm (nominal) diameter. In the case of prior art of metallic fixation devices 5 mm applicators are universally employed. Since it is not clear that the medical advantages of the use of absorbable fasteners would totally out weigh the disadvantages of moving to a 10 mm applicator it must be assumed that absorbable fasteners must also employ 5 mm applicators. Because of the lower strength of absorbable material this requirement imposes severe design constraints on both the applier and the fastener. 
     Implanted mesh fasteners are subjected to pull out forces from a number of sources. Non-porous mesh can be subjected to forces perpendicular to the abdominal wall by interabdominal pressure increases such as experienced during sneezing or coughing. These increased forces on the mesh are rather small however and non-existent for porous mesh. Most meshes in use today have a tendency to shrink after implant. The forces resulting from the shrinkage is, primarily, parallel to the abdominal surface and results in high shear and tensile forces on the fasteners. These forces can result in fixation failure. The fastener can fracture, separating the mesh holding feature from the tissue-snaring feature or it can pull out of the tissue owing to inadequate tissue snaring. Alternately, helical wire fasteners can unwind and offer little resistance to pull out. The shape metal anchor is inserted through a large needle hole and since it is flexible and very narrow in one dimension it can separate from the mesh owing to the mesh anchor arms bending upwards and threading back through the large insertion hole. The anchor often remains lodged in the tissue while separating from the mesh in this manner. 
     The strength and flexibility of the fastener material are of major importance in the design considerations of the applicator, particularly in the case of fasteners formed from polymers. Ory, et al (U.S. Pat. No. 6,692,506) teaches the use of L Lactic Acid polymer. Ory discloses adequate fixation strengths but the applicator device required to insert his fastener is necessarily 10 mm in diameter thereby causing the procedure to be more invasive than necessary. Ory further discloses a hollow needle with a large outside diameter, through which the fastener is inserted, that forms a rather large hole in the mesh and tissue to supply adequate columnar strength for penetration of the fastener. Entry holes of this size can give rise to multiple small hernias know as Swiss cheese hernias. 
     Absorption Time 
     There are two forms of PL, one synthesized from the d optical isomer and the other from the l optical isomer. These are sometimes designated DPL and LPL. A polymer with 50-50 random mixture of L and D is herein designated DLPL. 
     High molecular weight homo and co-polymers of PG and PL exhibit absorption times ranging from 1 month to greater than 24 months. Homo crystalline PG and PL generally require greater than 6 months to absorb and thus are not optimum materials for hernia mesh fixation. Amorphous co-polymers of PG and PL, on the other hand, typically degrade in less than 6 months and are preferably used in the present invention. For high molecular weight co-polymers of PG and PL the actual absorption time is dependent on the molar ratio and the residual monomer content. For a given monomer residual the absorption time varies from about 1 month to about 5 months as the molar content of DLPL increases from 50 to 85 percent with PG decreasing from 50 to 15 percent. Co-polymers of DLPL and PG in the molar range of 50 to 85 percent of DLPL are preferred for this invention. The geometry of the fastener also effects the absorption time. Smaller high surface area devices absorb faster. 
     The time required for the human body to react to the foreign body of the mesh for tissue ingrowth into the mesh is typically 10 days. However, mesh migration and mesh contraction can occur for more than two months if not adequately stabilized. Since fixation fasteners can impinge upon nerves and cause pain it is desirable for the fasteners to be absorbed as soon as possible after the tissue ingrowth and after the mesh is secure against migration or contraction. For most absorbable materials there is a difference between the time for loss of fixation strength and mass loss. Fixation strength decreases quicker than fastener mass owing to some degree of crystalline structure in the polymer. For these reasons the preferred absorption time for the current invention is 3-5 months after implant. 
     Absorption time can be effected by radiation sterilization. This must be taken into account when formulating the polymer if radiation sterilization is to be used. For large sterilization doses polymers may have to be formulated with longer than needed absorption times prior to radiation sterilization so that the desired absorption time is obtain after sterilization since radiation, generally, tends to reduce absorption time. 
     Temperature Effects 
     Glass transition temperature (Tg) is the temperature above which a polymer becomes soft, can loose its shape, and upon re-cooling can shrink considerably. Both crystalline and amorphous polymers exhibit glass transitions in a temperature range that depends on the mobility of the molecules, which is effected by a number of factors such as molecular weight and the amount of residual monomers. Glass transition temperatures range from about 43 to 55 degrees centigrade (deg. C.) for co-polymers of PG and DLPL. Where as 100% PG has a Tg of 35-40 deg. C. and 100% PL exhibits a Tg from 50-60 deg. C. Since the core temperature of the body can reach 40 degrees C. the preferred Tg for the material comprising the current invention is greater than 40 deg. C. In addition hernia mesh fasteners are often manufactured and shipped via surface transportation under uncontrolled, extreme heat conditions. Temperatures in commercial shipping compartments in the summer can exceed 60 degrees C. It is necessary to provide thermal protection in the packaging so that the fastener temperature does not exceed its Tg. 
     Sterilization and Packaging 
     Bio-absorbable polymers degrade when exposed to high humidity and temperature. Autoclaving cannot be used, for example. Most ethylene oxide (ETO) sterilization processes employ steam and high temperatures (above Tg) to obtain reasonable “kill” times for the bio-burden commonly found on the device. High doses of gamma radiation or electron beam radiation (E Bream), both accepted methods of sterilization for many devices, could weaken the mechanical properties of PG, PL and their co-polymers. It is therefore necessary during the manufacturing process of the fastener and its applicator to maintain cleanliness to a high degree such that the bio-burden of the components is small enough so that pathogens are adequately eradicated with less severe forms of sterilization. 
     Radiation doses above 25 kilogray (kgy) are known to lessen the mechanical strength of bio-absorbable polymers whereas some pathogens are known to resist radiation doses below 10 kgy. It is necessary, for the preferred embodiment of the present invention, during manufacturing to keep the pathogen count below a certain threshold to insure the accepted regulatory standards are met for radiation levels between 10 and 25 kgy. 
     In a second embodiment of the present invention it is necessary during manufacturing to keep the pathogen count below a certain threshold to insure the accepted regulatory standards are obtained for sterilization using a non-steam, low temperature, ethylene oxide (ETO) process below Tg of the fastener polymer. 
     Fasteners of the present invention must be carefully packaged to maintain adequate shelf life prior to use. Care must be taken to hermetically seal the device and to either vacuum pack, flood the package with a non-reactive dry gas prior to sealing, or to pack the device with a desiccant to absorb any water vapor since hydrolysis breaks down the backbone of the co-polymers. 
     ETO sterilization requires the gas to contact the device to be sterilized. Devices that are not humidity sensitive can be packaged in a breathable packaging material so that ETO can diffuse in, and after sterilization, diffuse out so that the device can be sterilized without unsealing the packaging. For the alternate embodiment of the present invention the device must be hermetically sealed after sterilization with ETO. Since gamma radiation and electron beam radiation sterilization can be accomplished through hermetically sealed packaging without disturbing the seal, either of these two sterilization processes is employed for the preferred embodiment of the present invention. 
     Ory, et al (U.S. Pat. No. 6,692,506), Criscuolo, et al (US application 20040092937), Phillips (U.S. Pat. Nos. 5,203,864 and 5,290,297), Kayan (U.S. application 20040204723), and Shipp (U.S. application Ser. Nos. 10/709,297, 10/905,020, and 10/907,834) have suggested the use of bio-absorbable materials for use as hernia mesh fixation devices to solve the problems associated with the permanency of metal implants. Ory, preferably, suggests forming the fixation device from LPL but the absorption time for LPL can exceed two years, much longer than optimum for hernia fixation devices since the lessening of pain depends on mass loss of the device. While Phillips and Kayan advocate the use of bio-absorbable material to form the fastener neither teach any details or methods for effectuating such a device. Criscuolo suggests the use of PG and PL with an absorption time of 2-3 weeks but does not disclose a method of forming the device that results in such an absorption time. In any respect, migration and contraction of the mesh has been documented to occur up to 8 weeks after implant. Loss of fixation after 2 to 3 weeks could well lead to hernia recurrence. 
     Hernia mesh such as PTFE based mesh manufactured by W. L. Gore is difficult to penetrate since the material is tough, non macro-porous, and relative inelastic. Attempts to penetrate these types of meshes with a puncture type applicator result in the mesh indenting into the tissue to a significant depth prior to penetration, especially for soft tissue. This indentation sometimes allows the tissue penetrator means, often a hollow needle, to penetrate through the abdomen wall and into the surgeon&#39;s hand, thus exposing the surgeon to potential hepatitis and AIDS viruses. The fastener of the present invention is equipped with screw threads that easily penetrate tough, non macro-porous, and relative inelastic mesh with a minimum of indentation. Once the threads are screwed through the mesh the underlying tissue is pull toward the mesh by the threads rather than push away from the mesh as is the case with puncture type devices. 
     Details of the method of manufacturing the improved fastener are herein provided. 
     What is needed then is an absorbable mesh fixation fastener and a method of forming an absorbable mesh fixation fastener that exhibits a known absorption time and that exhibits the mechanical properties adequate for the desired fixation strength and the required implant forces. 
     What is also needed is a method of packaging an absorbable mesh fixation device and the delivery device that minimizes the effects of high ambient shipping temperatures and humidity. 
     What is also needed is a method of sterilization of an absorbable mesh fixation fastener and its delivery device that has minimal effect on their physical properties, particularly the fastener. 
     What is further needed then is an absorbable mesh fixation fastener of improved geometry that easily penetrates tough, non macro-porous, and relatively inelastic mesh with minimal indentation to minimize the possibility of the fastener breaching the abdominal wall. 
     SUMMARY OF THE INVENTION 
     A method of producing and deploying a bio-absorbable hernia mesh fixation fastener exhibiting an in vivo absorption time between 1.5 and 13 months and its method of use is disclosed. A method of sterilization and a method of packaging the fastener to retain the critical physical properties of the fastener prior to implantation are also disclosed. The hernia mesh fixation device of the present invention is, preferably, injection molded using any of a variety of mole fractions of d, l-lactide and glycolide co-polymers, depending upon the desired absorption time, and mechanical properties. Preferably the mole ratio is 75-25 percent d, l lactide to glycolide yielding an absorption time after implant of 4-5 months and a glass transition temperature of 49 Deg. C. The modulus of elasticity of the preferred embodiment is 192,000 PSI and the tensile strength is 7200 PSI after injection molding at 150 Deg. C. 
     The fastener of the present invention comprises a head with a threaded portion and a slotted portion, a truncated, threaded tissue-snaring section that, upon rotation, easily penetrates tough, non macro-porous, and relative inelastic mesh and pulls underlying tissue toward the head of the fastener, firmly anchoring the mesh to the tissue and thus avoiding excessive indentation of the abdominal wall during deployment. 
     The fastener deliver device, or applier, of the present invention has a longitudinal axis, a proximal body, a handle, a rotator, a fastener retainer, a fastener advancer, a force reactor, and an fastener ejector. 
     Sterilization standards by the U.S. FDA allow radiation doses less than 25 kgy provided the bio-burden is below 1000 colony forming units (CFU). The components of the delivery device and the fasteners of the present invention are manufactured and assembled under clean room conditions such the bio-burden is well below 1000 CFUs. This allows gamma and E Beam sterilization with doses below the damage threshold of the preferred co-polymers of DLPL and PG, 25 kgy. Mechanical properties of the injected molded fastener of the present invention have been retested after dosing with 25 kgy E Beam. The same values of flex modulus and tensile strength were measured before and after dosing. Gamma or E Beam is the preferred sterilization process, however, an alternate embodiment comprises sterilization employing ethylene oxide without the use of steam and dosed at a temperature below the glass transition temperature. 
     For the preferred embodiment of the present invention the delivery device loaded with fasteners is first sealed into a vacuum formed tray with a breathable Tyvek (a registered trademark of DuPont) lid. This tray is then further hermetically sealed into a foil pouch. The foil pouch is then placed inside an insulated shipping container. The insulation is adequate to assure that the temperature of the fastener remains below 30 deg. C. after exposure to severe heat conditions sometimes experienced during shipping. Gamma or E Beam sterilization is accomplished by radiation through the shipping container. 
     In an alternate embodiment the sealed vacuum formed tray is placed into the hermetically sealed foil pouch after ETO sterilization. The ETO will penetrate the breathable lid. After the ETO process the device is sealed into the foil pouch and the pouch is placed into the thermally insulated container described above for shipping. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of the fastener according to the present invention. 
         FIG. 2  is the distal end view of the fastener according to the present invention. 
         FIG. 3  depicts the fastener fixating mesh to tissue. 
         FIG. 4  is a cutaway view of the proximal end of the applier according to the present invention. 
         FIG. 5  is a cutaway view of the distal end of the applier according to the present invention. 
         FIG. 6  is an enlargement of a cutaway view of the distal end of the applier according to the present invention. 
         FIG. 7 a    is a side profile of fastener thread cutter. 
         FIG. 7 b    is a front profile of fastener thread cutter. 
         FIG. 8  depicts the side view of bevel gear with groove. 
         FIG. 9  is the anti-reversal drive device. 
     
    
    
     DETAILED DESCRIPTION 
     Turning now to  FIGS. 1, 2 and 3 , depictions of the fastener of the current invention, generally designated as  10 . Fastener  10  may be a non-cannulated fastener that comprises three sections, head section  11 , mesh retention section  12 , and threaded tissue-snaring section  13 . Head section  11  comprises two opposing head threads  17  and two opposing open or slotted sections  16 . The distal surface of head section  11  is formed onto the proximal end of mesh retention section  12 . The preferred maximum dimension of head  11  transverse to the longitudinal axis of fastener  10  is 5 mm. 
     Mesh retention section  12  may, alternately, be tapered or right-cylinder shaped or may be omitted, which would allow the proximal end of threaded tissue-snaring section  13  to abut the distal end of head section  11 . Unlike the embodiment of fastener  10  with no mesh retention section  12 , either the conical or cylindrical configuration mesh retention section  12  locks mesh  52  on to fastener  10  when mesh  52  is screwed past the proximal-most tissue-snaring thread  15   c  since there is no thread located in mesh retention section  12  that would allow mesh  52  to be unscrewed from fastener  10 . Mesh retention section  12  is generally cylindrical or conical shaped with a dimension transverse to its longitudinal axis that is smaller than the transverse dimension of head  11  and the transverse dimension of proximal most tissue-snaring thread  15   c . Preferably the dimension transverse to the mesh retention section  12  longitudinal axis is 1 and 1.5 mm and the dimension parallel to the longitudinal axis is preferably between 0.5 and 1.5 mm. 
     Threaded tissue-snaring section  13  comprises aggressive, auger-like threads peaks,  15   a ,  15   b  and  15   c . Threads  13  spiral in either a right hand or left hand manner (here shown right hand) from the distal end of mesh retention section  12  to the distal surface  14  of fastener  10  with, preferably, three thread peaks  15   a ,  15   b , and  15   c  and two thread roots  19  band  19   a.    
       FIG. 8  depicts a preferred embodiment of a tool steel thread cutter  60  for cutting thread section  13 . Cutter  60  comprises a mounting shank  63  of diameter D and cutter section  62 . Tapering a length of cylinder with angle theta and then removing half the tapered material to the centerline of the cylinder as depicted in  FIGS. 7 a  and 7 b    results in forming cutting section  62 . Radii  61  and  66  preferably are ground on the tip of cutter section  62 . Preferably, theta is 20 degrees, D is 4.8 mm, L is 5.8 mm and radii  61  and  63  are 0.5 mm. 
     Thread section  13  can be formed by securing, preferably, a cylinder of absorbable polymer material, 5 mm diameter in diameter to one rotating axis of a three-axis machine center. Cutter  60  is chucked into a spindle and rotated at a speed appropriate for cutting the material on to which thread section  13  is to be cut. The longitudinal axis of cutter  60  is perpendicular to the longitudinal axis of the cylinder. The distal tip of cutter  60  is initially positioned on the centerline of the cylinder at a distance X from the distal surface of the cylinder. The machine center is then programmed to translate cutter  60  away from the cylinder&#39;s axis, which is rotated about the longitudinal axis, and simultaneous to move the cutter proximal. By starting the cutter distal of the cylinder, but on the centerline, the auger-type thread section  13  are formed. Any partial threads that occupy the mesh retention section  12  are then milled out so that mesh retention section  12  is preferably circular in cross section. Preferably, X is set to 0.75 mm and the machine center axis parallel to the cylinder axis is translated at a rate five times the rate at which cutter  60  is translated perpendicular to the cylinder axis. Preferably the cylinder is rotated four revolutions as cutter  60  moves from the starting position to just short of the distal surface of head  11 . This process forms threads as depicted in  FIG. 1 . A similar, but mirrored process, can be employed to form electrodes for burning a cavity into each half of an injection mold. Care must be taken to insure surface  14  is sharp to insure fastener  10  easily penetrates tough mesh material such as expanded PTFE. Fastener  10  is then completed by cutting the partial head threads  17  using process well know in the art. 
     First thread peak  15   c  is formed at the distal end of mesh retention section  12  and is smaller in dimensions transverse to the longitudinal axis than head section  11  and larger than mesh retention section  12  in dimensions transverse to the axis. The preferred transverse dimensions are 3.7 mm and 1.1 mm of the first thread peak  15   c  and the first root  19   b  respectively. The preferred transverse dimensions for second thread peak  15   b  and second thread root  19   a  are 2.9 mm and 0.4 mm respectively. The preferred transverse dimension of third thread peak  15   a  is 1.5 mm. 
     Distal surface  14  is the terminus of tissue-snaring section  13 . Owing to the process described above threads  18  terminate distally prior to reaching an apex. The dimension D shown in  FIG. 1  is the transverse dimension of the distal most thread  15   a  of threaded tissue-snaring section  13 . D should be as large as design constraints will allow, preferably, greater than 1 mm. This geometry allows for ease of mesh penetration and minimizes indentation of the mesh into soft tissue as compared to a pointed distal end. A larger value of D, results in less pressure to cause indentation of tissue  51  and mesh  52 , for a given distal force exerted on applier  20  by the surgeon. 
     Turning now to Turning now to  FIGS. 4, 5, and 6  depicting the delivery device, or applier, for mesh fastener  10 , generally designated as  20 .  FIG. 4  is a cutaway view of the proximal end or body  35  of applier  20 . Body  35  of applier  20  comprises handle  21 , outer tube  22  stabilizer ribs  36 , inner tube  23 , trigger  24  with trigger gear  32  and trigger pivot  34  attached to handle  21 , bevel gear  25 , return spring  26 , pinion gear  27 , anti reversal drive  28 , and bevel pinion gear  29 . Pivot  34  is fixedly mounted to handle section  21  of body  35  and the axial for pinion  27  and bevel  25  is fixedly mounted to body  35 . Drive  28  is fixed to pinion  27  owing to spline hub  40  that is fixedly attached to pinion  27 . Drive  28  rotates bevel  25  owing to drive tooth  41  depicted in  FIG. 9  mating into groove  33  in bevel  25  shown in  FIG. 8 . 
       FIG. 5  depicts the distal end  30  of applier  20  with twenty fasteners  10  loaded, ready for use. 
       FIG. 6  is cutaway view of an enlargement of the distal end  30  of applier  20  depicting the distal most five fasteners  10 . Head threads  17  of fasteners  10  engage internal screw threads  38  in outer tube  22 . The distal end of inner tube  23  is slotted to accept multiple fasteners  10 , having two tines opposite the two slots, not shown because of the cutaway, that engage two fastener slots  16 . Head threads  17  extend between the tines to engage outer tube threads  38 . Rotation of inner tube  23  about its longitudinal axis rotates fasteners  10  and advances them distally owing to head threads  17  engagement with outer tube threads  38 . In the preferred embodiment fasteners  10  are not in forced engagement with each other to avoid damage to distal tip  14  of fasteners  10 . 
     In a preferred embodiment there are twenty-four tube threads  38  per inch, the overall length of fastener  10  is 0.203 inches, with five full turns of inner tube  23  advancing fasteners  10  0.208 inches. The distal end of outer tube  22  comprises counter bored  39  that preferably has a depth of 0.030 inches, which allows distal most fastener  10  to release from outer tube threads  38  in the last three quarters of a turn of a five turn actuation sequence in the application and ejection process, as will be detailed below. 
     Five embodiments of fastener  10  are described herein comprising four different molar ratios of DLPL and PG. The resins of the co-polymers in each case were prepared using well-known techniques of polymerization of cyclic dimmers. The molar percentages (M) of DLPL and PG were measured along with the residual monomer percentage (RM). After polymerization the resins were thoroughly dried. Fastener  10  was then injection molded in a standard micro-molding machine at 150 Deg. C. The transition glass temperature (Tg), the absorption time at 37 Deg. C. (to 20% of the original mass) (AT), the tensile strength (TS) and Young&#39;s modulus (YM) were then measured. Fastener  10  was then subjected to 25 kgy E Beam radiation and the tensile strength and Young&#39;s modulus re-measured. Standard techniques, well known by those skilled in the art, were employed in the measurements of each of the parameters. The results are shown below: 
     
       
         
               
             
               
               
               
               
               
               
               
               
             
           
               
                   
               
               
                 Case I 
               
             
          
           
               
                   
                 M, 
                 M, 
                   
                   
                   
                   
                   
               
               
                   
                 DLPL, 
                 PG, 
                 RM, 
                 Tg, 
                 AT, 
                   
                 YN, 
               
               
                 Parameter 
                 % 
                 % 
                 % 
                 Deg. C. 
                 Months 
                 TS, PSI 
                 PSI 
               
               
                   
               
               
                   
                 100 
                 0 
                 2.1 
                 49.4 
                 13 
                 6100 
                 206,000 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
               
               
             
           
               
                   
               
               
                 Case II 
               
             
          
           
               
                   
                 M, 
                 M, 
                   
                   
                   
                   
                   
               
               
                   
                 DLPL, 
                 PG, 
                 RM, 
                 Tg, 
                 AT, 
                   
                 YN, 
               
               
                 Parameter 
                 % 
                 % 
                 % 
                 Deg. C. 
                 Months 
                 TS, PSI 
                 PSI 
               
               
                   
               
               
                   
                 85 
                 15 
                 2.1 
                 49.7 
                 5.8 
                 7900 
                 198,000 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
               
               
             
           
               
                   
               
               
                 Case III 
               
             
          
           
               
                   
                 M, 
                 M, 
                   
                   
                   
                   
                   
               
               
                   
                 DLPL, 
                 PG, 
                 RM, 
                 Tg, 
                 AT, 
                   
                 YN, 
               
               
                 Parameter 
                 % 
                 % 
                 % 
                 Deg. C. 
                 Months 
                 TS, PSI 
                 PSI 
               
               
                   
               
               
                   
                 75 
                 25 
                 1.6 
                 49.1 
                 4.3 
                 7200 
                 192,000 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
               
               
             
           
               
                   
               
               
                 Case IV 
               
             
          
           
               
                   
                 M, 
                 M, 
                   
                   
                   
                   
                   
               
               
                   
                 DLPL, 
                 PG, 
                 RM, 
                 Tg, 
                 AT, 
                   
                 YN, 
               
               
                 Parameter 
                 % 
                 % 
                 % 
                 Deg. C. 
                 Months 
                 TS, PSI 
                 PSI 
               
               
                   
               
               
                   
                 65 
                 35 
                 1.9 
                 47.2 
                 3.2 
                 74000 
                 190,000 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
               
               
             
           
               
                   
               
               
                 Case V 
               
             
          
           
               
                   
                 M, 
                 M, 
                   
                   
                   
                   
                   
               
               
                   
                 DLPL, 
                 PG, 
                 RM, 
                 Tg, 
                 AT, 
                   
                 YN, 
               
               
                 Parameter 
                 % 
                 % 
                 % 
                 Deg. C. 
                 Months 
                 TS, PSI 
                 PSI 
               
               
                   
               
               
                   
                 52 
                 48 
                 1.2 
                 46.7 
                 1.5 
                 8100 
                 188,000 
               
               
                   
               
             
          
         
       
     
     In each case retesting the tensile strength and Young&#39;s modulus after subjecting the fastener  10  to 25 kgy E Beam radiation yielded results statistically indistinguishable from the values in the tables above. 
     To design an appropriate insulated shipping container the historical average daily temperatures over a “hot weather route” from Florida to Arizona were obtained from www.engr.udayton.edu/weather. Heat flux data were determined from the historical data resulting in an insulation requirement of 2.5 inches of Cellofoam (a registered trademark of Cellofoam of North America, Inc.) with a thermal R-value of 3.86 per inch of thickness. Fasteners  10  were then shipped over the route packed in the insulated container and the internal temperature of a un-air conditioned cargo space of a roadway common carrier was measured during a five-day trip from Jacksonville Fla. to Phoenix Ariz. from Sep. 9 till Sep. 14, 2004. The internal temperatures of the cargo space, Tc, and the internal temperature of the insulated container, Ti, containing fasteners  10  were recorded every 30 minutes. The minimum and maximum temperatures in the cargo space and the insulated container are shown below: 
     
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Day 1 
                 Day 2 
                 Day 3 
                 Day 4 
                 Day 5 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Maximum Tc 
                 37 
                 34 
                 29 
                 48 
                 50 
               
               
                 Deg. C. 
               
               
                 Minimum Tc 
                 24 
                 18 
                 15 
                 27 
                 27 
               
               
                 Deg. C. 
               
               
                 Maximum Ti 
                 27 
                 27 
                 26 
                 27 
                 27 
               
               
                 Temperature, 
               
               
                 Deg. C. 
               
               
                 Minimum Ti 
                 24 
                 26 
                 21 
                 24 
                 24 
               
               
                 Temperature, 
               
               
                 Deg. C. 
               
               
                   
               
             
          
         
       
     
     Thus it is seen from the data above that the insulated shipping container is adequate for maintaining fastener  10  temperatures well below the glass transition temperature of 49 Deg. C. of the preferred co-polymer, 75/25 DLPL/PG, Case III above. 
     The preferred embodiment for the current invention is an injection molded fastener as depicted in  FIG. 1  comprising 75% DLPL, 25% PG, sterilized with radiation, either gamma or E Beam, at 25 kgy and packaged first in a hermetically sealed pack and an insulated shipping container. 
     Applier Loading and Operation 
     Multiple fasteners  10  are loaded onto the tines of inner tube  23  head to tail with distal end  14  pointed distally. Fasteners  10  are rotationally orientated such that the tines of inner tube  23  engage head slots  16 . The proximal end of the loaded inner tube assembly is inserted into the distal end of outer tube  22  until proximal-most fastener  10  encounters outer tube threads  38 . The inner tube assembly is then rotated until the distal end of inner tube  23  is flush with or slightly recessed into outer tube  22 . In this position the proximal end of inner tube  23  is proximal of the proximal end of outer tube  22 . Near the proximal end of inner tube  23  a drill through hole perpendicular to the longitudinal axis is located to accept bevel pinion pin  31  for securing bevel pinion  29  to inner tube  23 . The inner and outer tube assembly is then affixed into handle  21  with ribs  36  locking outer tube  22  against rotation or twisting in body  35 . Two clamshell halves are ultrasonic welded or otherwise fastened together to form body  35 . 
     Following sterilization loaded applier  20  is placed into a surgical field, usually through a 5 mm trocar, and the distal end of applier  20  is held firmly against mesh  52 , which covers tissue  51 . Outer tube threads  38  act as a force reactor to counter the distal force, generated by the screw-in process of the threaded tissue-snaring section  13 , so that fasteners  10  are unable to move proximally. Outer tube threads  38  engaging head threads  17  also restrain fasteners  10  from falling out of the distal end of applier  20  under the influence of gravity, for example. 
     Trigger  24  is then rotated clockwise about pivot  34  causing pinion  27  to rotate counterclockwise. Drive tooth  41  is engaged in groove  33  and thus rotates bevel  25  counterclockwise. Bevel  25  causes bevel pinion  29  to rotate clockwise (in right hand sense, conventionally). The gear train is sized such that full movement of trigger  24  gear teeth  32  causes 5 revolutions of bevel pinion  29  and hence 5 revolutions of inner tube  23 . This rotation of inner tube  23  rotates the stack of fasteners  10  five complete revolutions and advances them preferably 5.2 mm, the length of fastener  10 , owing to head threads  17  and the pitch of outer tube threads  38 , preferably 24 threads per inch. 
     As explained above rotation of inner tube  23  rotates fasteners  10 . Distal surface  14  of distal most-fastener  10  engages and penetrates mesh  52  and threaded tissue-snaring section  13  screws into and draws tissue  51  and mesh  52  together. During the last three quarters of a rotation of the five revolutions head threads  17  of distal most fastener  10  enter into counter bore  39 . Removal of the distal end  30  of applier  20  from mesh  52  releases distal-most fastener  10  and ejects it from applier  20 . Mesh  52  is thus affixed to tissue  51 . After the fastener screw-in process is complete trigger  24  is released, reset spring  26  returns trigger  24  with trigger gear  32  to its start, or home, position. This rotates pinion  27  and drive  28  clockwise. Flexible arm  37  allows drive tooth  41  to ride up out of groove  33  and rotate about the face of bevel  25  without bevel  25  rotating owing to greater friction of bevel  25  against its axial. Thus bevel  25 , bevel pinion  29 , inner tube  23 , and fasteners  10  do not rotate during the return stroke of applier  20  during the reset process leaving the stack of fasteners  10  forward with each remaining fastener moved distally one fastener length. The features of applier  20  describe herein assures that the plurality of fasteners  10  progress distally one fastener length and do not move proximal during the return stroke. At the end of the return stroke drive tooth  41  has rotated 360 degrees on the face of bevel  25  and it snaps back into groove  33  and in position to drive bevel  5 . Applier  20  is fully reset and ready for the deployment of the next fastener  10 . 
     From the foregoing, it will be appreciated that the absorbable fastener of the present invention functions to securely fasten tough, non macro-porous, and relative inelastic mesh to tissue. The fastener of the present invention will disintegrate after the body has secured the mesh against migration and contraction. The absorbable fastener of the present invention can be sterilized so that mechanical properties are maintained and it can be shipped under severe temperature conditions with insulated packaging so that the glass transition temperature is not exceeded. It will also be appreciated that the absorbable fastener of the present invention may be utilized in a number of applications such as hernia repair, bladder neck suspension, and implant drug delivery systems. 
     While several particular forms of the invention have been illustrated and described, it will be apparent by those skilled in the art that other modifications are within the scope and spirit of the present disclosure.