Buttress and Surgical Stapling Apparatus

[0001] 1. Technical Field

[0002] The present disclosure relates to surgical buttresses which can be releasably attached to a surgical stapling apparatus. The buttresses contain a porous layer and a non-porous layer.

[0003] 2. Background of Related Art

[0004] Surgical stapling devices have found widespread application in surgical operations where body tissue must be joined or removed. When operating on certain tissue, such as lung, esophageal, intestinal, duodenal, and vascular tissue, it is important to effectively seal the tissue which can be particularly prone to air or fluid leakage. Preventing or reducing air or fluid leakage can significantly decrease post operative recovery time. Thus, it would be advantageous to provide a material for use with a surgical stapling device which enhances sealing at the surgical wound site.

[0005] Buttresses having a porous layer and a non-porous layer are described herein. The multilayer buttresses are suitable for use in connection with a surgical stapling apparatus and assist in the sealing of tissue to prevent the leakage of fluids and gases. The surgical stapling apparatus includes a staple cartridge having a surface with at least one opening through which a staple may be ejected. The surgical stapling apparatus further includes an anvil having a surface against which an ejected staple may be deformed. A buttress in accordance with the present disclosure may be associated with either the staple cartridge, the anvil, or both.

[0006] In embodiments, the porous layer possesses haemostatic properties. In embodiments, the non-porous layer has anti-adhesion properties.

[0018] Embodiments of the presently disclosed multilayer buttress and surgical stapling apparatus will now be described in detail with reference to the drawing figures wherein like reference numerals identify similar or identical elements.

[0019] The multilayer surgical buttress described herein may be used in sealing a wound by approximating the edges of wound tissue between the staple cartridge and the staple anvil of a stapling apparatus which contains at least one multilayer surgical buttress having a non-porous layer and a porous layer and firing the stapling apparatus to force at least one staple to pass through the openings on the staple cartridge, at least one multilayer buttress, the tissue and the openings on the staple anvil to seal the tissue. Once stapled in place the porous layer advantageously reduces bleeding, assists in sealing the wound and allowing tissue ingrowth, if desired, while the non-porous layer provides support for the porous layer and may assist in preventing the formation of adhesions. In addition, the multilayer buttress may optionally include an additional reinforcement member (which, as described in more detailed below, may be absorbable or non-absorbable) to provide additional support to the multilayer buttress and assist in preventing tears during stapling.

[0020] It should be understood that buttresses need not be associated with both the staple cartridge and the anvil. Rather, a buttress may be associated with only the staple cartridge and not the anvil or with the anvil and not the staple cartridge. In addition, the multilayer surgical buttress described herein may be configured into any shape, size or dimension suitable to fit any surgical stapling, fastening or firing apparatus. Other examples of stapling apparatus which may utilize the multilayer buttress material described herein includes laparoscopic staplers (see, e.g., U.S. Pat. Nos. 6,330,965 and 6,241,139, the entire contents of which are incorporated herein by this reference), alternative stapling apparatus of the transverse anastomosis type for stapling a patient's mesentery (see, e.g., U.S. Pat. No. 5,964,394, the entire content of which is incorporated herein by this reference), and end-to-end anastomosis types for performing surgical anastomotic stapling with a circular cartridge and anvil mesentery (see, e.g., U.S. Pat. No. 5,915,616, the entire content of which is incorporated herein by this reference). The present buttresses may also be used in conjunction with instruments that apply two-part fasteners wherein a first part of the two-part fastener is stored in a cartridge or like member and can be fired and properly joined to a second part of the two-part fastener disposed in an anvil or like member. Those skilled in the art having read the present disclosure will readily envision how to adapt the present buttresses for use in connection with such apparatus and also envision other surgical apparatus with which the buttresses described herein may be used.

[0021] Now turning to FIGS. 3A and 3B, buttress 350 is shown having a non-porous layer 360 and a porous layer 370. It is envisioned that buttress 350 may contain a plurality of layers in which any combination of non-porous and porous layers may be configured. For example, a multilayer buttress may be formed in which multiple non-porous layers and porous layers are stacked in an alternating manner. In another example, the multilayer buttress may be formed in a “sandwich-like” manner wherein the outer layers of the multilayer buttress include porous layers and the inner layers are non-porous layers. It is further envisioned that the non-porous layer and porous layer may be positioned in any order relative to the surfaces of staple cartridge and staple anvil.

[0022] The non-porous layer of the buttress may be made from any biocompatible material. Thus, the non-porous layer of the multilayer buttress described herein may be formed from a natural material or a synthetic material. The material from which the non-porous layer is formed may be bioabsorbable or non-bioabsorbable. It should of course be understood that any combination of natural, synthetic, bioabsorbable and non-bioabsorbable materials may be used to form the non-porous layer. Some non-limiting examples of materials from which the non-porous layer may be made include but are not limited to poly(lactic acid), poly (glycolic acid), poly (hydroxybutyrate), poly (phosphazine), polyesters, polyethylene glycols, polyethylene oxides, polyacrylamides, polyhydroxyethylmethylacrylate, polyvinylpyrrolidone, polyvinyl alcohols, polyacrylic acid, polyacetate, polycaprolactone, polypropylene, aliphatic polyesters, glycerols, poly(amino acids), copoly (ether-esters), polyalkylene oxalates, polyamides, poly (iminocarbonates), polyalkylene oxalates, polyoxaesters, polyorthoesters, polyphosphazenes and copolymers, block copolymers, homopolymers, blends and combinations thereof.

[0023] In embodiments, natural biological polymers are used in forming the non-porous layer of the buttress. Suitable natural biological polymers include, but are not limited to, collagen, gelatin, fibrin, fibrinogen, elastin, keratin, albumin, hydroxyethyl cellulose, cellulose, oxidized cellulose, hydroxypropyl cellulose, carboxyethyl cellulose, carboxymethyl cellulose, chitan, chitosan, and combinations thereof. In addition, the natural biological polymers may be combined with any of the other polymeric materials described herein to produce the support layer of the buttress.

[0024] In embodiments, collagen of human and/or animal origin, e.g., type I porcine or bovine collagen, type I human collagen or type III human collagen, may be used to form the non-porous layer.

[0025] Native collagen may advantageously be used in acid solution or after processing, to eliminate the telopetpides, notably by pepsin digestion. The collagen, e.g., atelocollagen, can also be modified by oxidative cleavage by the use of periodic acid or one of its salts. The oxidative cleavage of the collagen allows for future moderate crosslinking in the collagenic material with other polymeric materials, macromolecular additives or the haemostatic agents contained in the haemostatic layer of the buttress.

[0026] In embodiments, the non-porous layer according to the present disclosure is made of collagen which is oxidized or a mixture in any proportions of non-oxidized and oxidized collagens.

[0027] In embodiments, at least one macromolecular additive may be combined with the collagen to provide a composition from which the non-porous layer is formed. Some examples of suitable macromolecular additives include, polyethylene glycol, glycerin, polysaccharides, dextran, maltodextrin, mucopolysaccharides, cellulose, alginate and combinations thereof. When used, the macromolecular additive may have a molecular weight of at least 3,000 Daltons and may represent a concentration from about 2 to 10 times less than the collagenic material present in the composition from which the non-porous layer is formed.

[0028] The non-porous layer may enhance the ability of the buttress to resist tears and perforations during the manufacturing, shipping, handling and stapling processes. Also, the non-porous layer may also retard or prevent tissue ingrowth from surrounding tissues thereby acting as an adhesion barrier and preventing the formation of unwanted scar tissue. Thus, in embodiments, the non-porous layer possesses anti-adhesion properties.

[0029] It is envisioned that the buttress may be releasably attached to the cartridge and/or the anvil in any manner capable of retaining the buttress in contact with the cartridge and/or the anvil prior to and during the stapling process, while allowing the buttress to be removed or released from the cartridge and/or the anvil following the penetration of the buttress by a surgical staple or other fastening device. For example, the buttress may be attached to the cartridge and/or the anvil using adhesives, sealants, glues, pins, tacks, tabs, clamps, channels, straps, protrusions and combinations thereof.

[0030] The non-porous layer may be formed using techniques within the purview of those skilled in the art, such as casting, molding and the like.

[0031] The porous layer of the buttress has openings or pores over at least a portion of a surface thereof. As described in more detail below, suitable materials for forming the porous layer include, but are not limited to fibrous structures (e.g., knitted structures, woven structures, non-woven structures, etc.) and/or foams (e.g., open or closed cell foams). In embodiments, the pores may be in sufficient number and size so as to interconnect across the entire thickness of the porous layer. Woven fabrics, knitted fabrics and open cell foam are illustrative examples of structures in which the pores can be in sufficient number and size so as to interconnect across the entire thickness of the porous layer. In embodiments, the pores do not interconnect across the entire thickness of the porous layer. Closed cell foam or fused non-woven materials are illustrative examples of structures in which the pores may not interconnect across the entire thickness of the porous layer. FIG. 5A schematically illustrates a foam porous layer wherein the pores span across the entire thickness of porous layer. In yet other embodiments, the pores do not extend across the entire thickness of the porous layer, but rather are present at a portion of the surface thereof. FIG. 5B schematically illustrates a porous layer wherein the pores do not span across the entire thickness thereof. In embodiments, the openings or pores are located on a portion of the surface of the porous layer, with other portions of the porous layer having a non-porous texture. FIG. 5C schematically illustrates a porous layer wherein the pores do not cover the entire surface of the porous layer, but rather are present on a central portion thereof. Those skilled in the art reading the present disclosure will envision other pore distribution patterns and configurations for the porous layer.

[0032] Where the porous layer is fibrous, the fibers may be filaments or threads suitable for knitting or weaving or may be staple fibers, such as those frequently used for preparing non-woven materials. The fibers may be made from any biocompatible material. Thus, the fibers may be formed from a natural material or a synthetic material. The material from which the fibers are formed may be bioabsorbable or non-bioabsorbable. It should of course be understood that any combination of natural, synthetic, bioabsorbable and non-bioabsorbable materials may be used to form the fibers. Some non-limiting examples of materials from which the fibers may be made include, but are not limited to poly(lactic acid), poly (glycolic acid), poly (hydroxybutyrate), poly (phosphazine), polyesters, polyethylene glycols, polyethylene oxides, polyacrylamides, polyhydroxyethylmethylacrylate, polyvinylpyrrolidone, polyvinyl alcohols, polyacrylic acid, polyacetate, polycaprolactone, polypropylene, aliphatic polyesters, glycerols, poly(amino acids), copoly (ether-esters), polyalkylene oxalates, polyamides, poly (iminocarbonates), polyalkylene oxalates, polyoxaesters, polyorthoesters, polyphosphazenes and copolymers, block copolymers, homopolymers, blends and combinations thereof.

[0033] Where the porous layer is fibrous, the porous layer may be formed using any method suitable to forming fibrous structures, including but not limited to knitting, weaving, non-woven techniques and the like. Suitable techniques for making fibrous structures are within the purview of those skilled in the art.

[0034] Where the porous layer is a foam, the porous layer may be formed using any method suitable to forming a foam or sponge including, but not limited to the lyophilization or freeze-drying of a composition. Suitable techniques for making foams are within the purview of those skilled in the art.

[0035] In embodiments, the porous layer possesses haemostatic properties. Illustrative examples of materials which may be used in providing the porous layer with the capacity to assist in stopping bleeding or hemorrhage include, but are not limited to, poly(lactic acid), poly(glycolic acid), poly(hydroxybutyrate), poly(caprolactone), poly(dioxanone), polyalkyleneoxides, copoly(ether-esters), collagen, gelatin, thrombin, fibrin, fibrinogen, fibronectin, elastin, albumin, hemoglobin, ovalbumin, polysaccharides, hyaluronic acid, chondroitin sulfate, hydroxyethyl starch, hydroxyethyl cellulose, cellulose, oxidized cellulose, hydroxypropyl cellulose, carboxyethyl cellulose, carboxymethyl cellulose, chitan, chitosan, agarose, maltose, maltodextrin, alginate, clotting factors, methacrylate, polyurethanes, cyanoacrylates, platelet agonists, vasoconstrictors, alum, calcium, RGD peptides, proteins, protamine sulfate, epsilon amino caproic acid, ferric sulfate, ferric subsulfates, ferric chloride, zinc, zinc chloride, aluminum chloride, aluminum sulfates, aluminum acetates, permanganates, tannins, bone wax, polyethylene glycols, fucans and combinations thereof.

[0036] Generally, the use of natural biological polymers, and in particular proteins, is particularly useful in forming porous layers having haemostatic properties. Suitable natural biological polymers include, but are not limited to, collagen, gelatin, fibrin, fibrinogen, elastin, keratin, albumin and combinations thereof. In such embodiments, the natural biological polymers may be combined with any other haemostatic agent to produce the porous layer of the buttress. The origin and types of collagens that may be used to form the porous layer are the same as those indicated above for the non-porous layer. However, the oxidized or non-oxidized collagen may be lyophilized, freeze-dried, or emulsified in the presence of a volume of air to create a foam and then freeze-dried, to form a porous compress.

[0037] In embodiments, the porous layer may be made from denatured collagen or collagen which has at least partially lost its helical structure through heating or any other method, consisting mainly of non-hydrated a chains, of molecular weight close to 100 kDa. The term “denatured collagen” means collagen which has lost its helical structure. The collagen used for the porous layer as described herein may be native collagen or atellocollagen, notably as obtained through pepsin digestion and/or after moderate heating as defined previously. The collagen may have been previously chemically modified by oxidation, methylation, succinylation, ethylation or any other known process.

[0038] In embodiments, the porous layer can be obtained by freeze-drying an aqueous acid solution or suspension of collagen at a concentration of about 2 to about 50 g/l and at an initial temperature of about 4 to about 25° C. The concentration of collagen in the solution can be from about 1 g/l to about 30 g/l and in embodiments about 10 g/l. This solution is advantageously neutralized to a pH of about 6 to about 8.

[0039] In embodiments, the porous layer can be at least 0.1 cm thick. In embodiments the thickness of the porous layer can range from about 0.2 to about 1.5 cm thick. The porous layer can have a density of not more than about 75 mg collagen/cm² and in embodiments below about 7 mg collagen/cm². The size of the pores in the porous layer can be from about 20 μm to about 200 μm, in embodiments from about 100 μm to about 200 μm.

[0040] The haemostatic agents from which the porous layer can be made or which can be included in the porous layer can be in the form of foams, fibers, filaments, meshes, woven and non-woven webs, compresses, pads, powders, flakes, particles and combinations thereof. In embodiments, the porous layer having haemostatic properties provides to the multilayer buttress when hydrated characteristics similar to that of the tissue to which the buttress is applied.

[0041] The multilayer buttress material described herein may be formed using any method known to those skilled in the art capable of connecting a non-porous layer to a porous layer. It is envisioned that the non-porous layer and the porous layer may be adhered to one another using chemical bonding, surgical adhesives, surgical sealants, and surgical glues. In addition, the layers may be bound together using mechanic means such as pins, rods, screws, clips, etc. Still further, the layers may naturally or through chemical or photoinitiation may interact and crosslink or provide covalent bonding between the layers.

[0042] In embodiments, the multilayer buttress described herein is prepared by attaching the individual layers of materials together to form a multiple layer buttress. The porous layer may be formed separate and apart from the non-porous layer. Alternatively, the porous and non-porous layers may be formed together.

[0043] In some embodiments, the porous layer may be attached to the non-porous layer, in a manner which allows the two layers to crosslink and form a chemical bond creating a multilayer buttress material capable of sealing tissue. One such example includes pouring a solution of the material from which the non-porous layer is to be made into a mold and applying the porous layer to the poured solution during the gelification process. As described in U.S. Pat. No. 6,596,304, which the entire content of which is incorporated herein by reference, the porous layer may contain a porous compress made from collagen. The non-porous layer may be made from a biopolymer film containing collagen, polyethylene and glycerol. The porous layer may be added to the non-porous film and allowed to crosslink to form multilayer material suitable for reinforcing a staple or suture line.

[0044] As further shown in FIGS. 3A and 3B, buttress 350 may also include a reinforcement member 380. In FIG. 3A, reinforcement member 380 is shown being positioned between non-porous layer 360 and porous layer 370 of buttress 350 and in FIG. 3B, reinforcement member 380 is shown being positioned solely within an individual layer, supporting in this case non-porous layer 360 of buttress 350. It is envisioned that reinforcement member 380 may also be positioned within the porous layer. The reinforcement member may also be positioned at the surface of one of the layers making up the multilayer buttress and, in embodiments, may be positioned at an exterior surface of the multilayer buttress.

[0045] Some suitable non-limiting examples of the reinforcement member include meshes, monofilaments, multifilament braids, chopped fibers (sometimes referred to in the art as staple fibers) and combinations thereof.

[0046] Where the reinforcement member is a mesh, it may be prepared using any technique known to those skilled in the art, such as knitting, weaving, tatting, knipling or the like.

[0047] Where monofilaments or multifilament braids are used as the reinforcement member, the monofilaments or multifilament braids may be oriented in any desired manner. For example, the monofilaments or multifilament braids may be randomly positioned with respect to each other within the buttress structure. As another example, the monofilaments or multifilament braids may be oriented in a common direction within the buttress. In embodiments, monofilaments or multifilament braids are associated with both the porous layer and with the non-porous layer. In an illustrative embodiment of this type shown in FIG. 3C, buttress 350 includes a first reinforcement member 381 having a plurality of reinforcement members oriented in a first direction within the non-porous layer 360 and a second reinforcement layer 382 having a plurality of reinforcement members oriented in a second direction within the porous layer 370. In embodiments, the first and second directions may be substantially perpendicular to each other as seen in FIG. 3C.

[0048] Where chopped fibers are used as the reinforcement member, the chopped fibers may be oriented in any desired manner. For example, the chopped fibers may be randomly oriented or may be oriented in a common direction. The chopped fibers can thus form a non-woven material, such as a mat or a felt. The chopped fibers may be joined together (e.g., by heat fusing) or they may be unattached to each other. The chopped fibers may be of any suitable length. For example, the chopped may be from 0.1 mm to 100 mm in length, in embodiments, 0.4 mm to 50 mm in length. FIG. 3D shows an illustrative embodiment wherein buttress 350 has chopped fibers 380 incorporated in non-porous layer 360 which can be applied to porous layer 370.

[0049] It is envisioned that the reinforcement member may be formed from any bioabsorbable, non-bioabsorbable, natural, and synthetic material previously described herein including derivatives, salts and combinations thereof. In particularly useful embodiments, the reinforcement member may be made from a non-bioabsorbable material to provide long term flexible tissue support. In embodiments, the reinforcement member is a surgical mesh made from polypropylene or polylactic acid. In addition polyethylene materials may also be incorporated into the buttress described herein to add stiffness. Where monofilaments or multifilament braids are used as the reinforcement member, any commercially available suture material may advantageously be employed as the reinforcement member.

[0050] Turning now to FIG. 4, one embodiment is shown in which multilayer buttress 350 includes at least one hole 390 which is shaped and designed to frictionally fit onto at least one pin 400 located on staple cartridge 104 and/or staple anvil 204. Hole 390 and pin 400 are designed to releasably attach multilayer buttress 350 to staple cartridge 104 and/or staple anvil 204 and both can be of any size, shape or dimension.

[0051] In some embodiments, at least one bioactive agent may be combined with the buttress material and/or any of the individual components (the porous layer, the non-porous layer and/or the reinforcement member) used to construct the buttress material. In these embodiments, the buttress material can also serve as a vehicle for delivery of the bioactive agent. The term “bioactive agent”, as used herein, is used in its broadest sense and includes any substance or mixture of substances that have clinical use. Consequently, bioactive agents may or may not have pharmacological activity per se, e.g., a dye, or fragrance. Alternatively a bioactive agent could be any agent which provides a therapeutic or prophylactic effect, a compound that affects or participates in tissue growth, cell growth, cell differentiation, an anti-adhesive compound, a compound that may be able to invoke a biological action such as an immune response, or could play any other role in one or more biological processes. It is envisioned that the bioactive agent may be applied to the medial device in any suitable form of matter, e.g., films, powders, liquids, gels and the like.

[0052] Examples of classes of bioactive agents which may be utilized in accordance with the present disclosure include anti-adhesives, antimicrobials, analgesics, antipyretics, anesthetics, antiepileptics, antihistamines, anti-inflammatories, cardiovascular drugs, diagnostic agents, sympathomimetics, cholinomimetics, antimuscarinics, antispasmodics, hormones, growth factors, muscle relaxants, adrenergic neuron blockers, antineoplastics, immunogenic agents, immunosuppressants, gastrointestinal drugs, diuretics, steroids, lipids, lipopolysaccharides, polysaccharides, and enzymes. It is also intended that combinations of bioactive agents may be used.

[0053] Anti-adhesive agents can be used to prevent adhesions from forming between the implantable medical device and the surrounding tissues opposite the target tissue. In addition, anti-adhesive agents may be used to prevent adhesions from forming between the coated implantable medical device and the packaging material. Some examples of these agents include, but are not limited to poly(vinyl pyrrolidone), carboxymethyl cellulose, hyaluronic acid, polyethylene oxide, poly vinyl alcohols and combinations thereof.

[0054] Suitable antimicrobial agents which may be included as a bioactive agent in the bioactive coating of the present disclosure include triclosan, also known as 2,4,4′-trichloro-2′-hydroxydiphenyl ether, chlorhexidine and its salts, including chlorhexidine acetate, chlorhexidine gluconate, chlorhexidine hydrochloride, and chlorhexidine sulfate, silver and its salts, including silver acetate, silver benzoate, silver carbonate, silver citrate, silver iodate, silver iodide, silver lactate, silver laurate, silver nitrate, silver oxide, silver palmitate, silver protein, and silver sulfadiazine, polymyxin, tetracycline, aminoglycosides, such as tobramycin and gentamicin, rifampicin, bacitracin, neomycin, chloramphenicol, miconazole, quinolones such as oxolinic acid, norfloxacin, nalidixic acid, pefloxacin, enoxacin and ciprofloxacin, penicillins such as oxacillin and pipracil, nonoxynol 9, fusidic acid, cephalosporins, and combinations thereof. In addition, antimicrobial proteins and peptides such as bovine lactoferrin, lactoferricin B and antimicrobial polysaccharides such as fucans and derivatives may be included as a bioactive agent in the bioactive coating of the present disclosure.

[0055] Other bioactive agents which may be included as a bioactive agent in the coating composition applied in accordance with the present disclosure include: local anesthetics; non-steroidal antifertility agents; parasympathomimetic agents; psychotherapeutic agents; tranquilizers; decongestants; sedative hypnotics; steroids; sulfonamides; sympathomimetic agents; vaccines; vitamins; antimalarials; anti-migraine agents; anti-parkinson agents such as L-dopa; anti-spasmodics; anticholinergic agents (e.g. oxybutynin); antitussives; bronchodilators; cardiovascular agents such as coronary vasodilators and nitroglycerin; alkaloids; analgesics; narcotics such as codeine, dihydrocodeinone, meperidine, morphine and the like; non-narcotics such as salicylates, aspirin, acetaminophen, d-propoxyphene and the like; opioid receptor antagonists, such as naltrexone and naloxone; anti-cancer agents; anti-convulsants; anti-emetics; antihistamines; anti-inflammatory agents such as hormonal agents, hydrocortisone, prednisolone, prednisone, non-hormonal agents, allopurinol, indomethacin, phenylbutazone and the like; prostaglandins and cytotoxic drugs; estrogens; antibacterials; antibiotics; anti-fungals; anti-virals; anticoagulants; anticonvulsants; antidepressants; antihistamines; and immunological agents.

[0056] Other examples of suitable bioactive agents which may be included in the coating composition include viruses and cells, peptides, polypeptides and proteins, analogs, muteins, and active fragments thereof, such as immunoglobulins, antibodies, cytokines (e.g. lymphokines, monokines, chemokines), blood clotting factors, hemopoietic factors, interleukins (IL-2, IL-3, IL-4, IL-6), interferons (β-IFN, (α-IFN and γ-IFN), erythropoietin, nucleases, tumor necrosis factor, colony stimulating factors (e.g., GCSF, GM-CSF, MCSF), insulin, anti-tumor agents and tumor suppressors, blood proteins, gonadotropins (e.g., FSH, LH, CG, etc.), hormones and hormone analogs (e.g., growth hormone), vaccines (e.g., tumoral, bacterial and viral antigens); somatostatin; antigens; blood coagulation factors; growth factors (e.g., nerve growth factor, insulin-like growth factor); protein inhibitors, protein antagonists, and protein agonists; nucleic acids, such as antisense molecules, DNA and RNA; oligonucleotides; polynucleotides; and ribozymes.

[0057] Type I porcine collagen is extracted from pig dermis and rendered soluble through pepsin digestion and purified by saline precipitation.

[0058] A 10 g/l solution of the collagen is prepared by dissolving 23 g of damp collagen (12% humidity) in 2070 g of ultrafiltered water, at an ambient temperature below 25° C. It is neutralized using sodium hydroxide to a neutral pH, which leads to precipitation of the collagen.

[0059] A porous layer suitable for use in making a multilayer buttress is prepared by poring the suspension onto freeze-dry plates, with 0.5 to 1 g/cm² and freeze-drying, using one cycle lasting about 24 hours.

[0060] Optionally, in a variant, the freeze-dried porous layer so produced can be heated to 60° C. for several hours (4 to 15), which provides it with better cohesion and mechanical resistance in certain applications.

[0061] Type I porcine collagen is extracted from pig dermis and rendered soluble through pepsin digestion and purified by saline precipitation.

[0062] A 30 g/l solution of oxidized collagen used for this example, is prepared according to patent FR-A-2 715 309.

[0063] Dry collagen fibres are used for preference, obtained by precipitation of an acid solution of collagen by adding NaCl, then washing and drying the precipitate obtained using aqueous solutions of acetone in concentrations increasing from 80% to 100%.

[0064] A 30 g/l solution of collagen is prepared by dissolving it in 0.01 N HCl. Its volume is 49 liters. Periodic acid is added to it at a final concentration of 8 mM, i.e. 1.83 g/l. Oxidation takes place at an ambient temperature close to 22° C. for 3 hours away from light.

[0065] Then an equal volume of a solution of sodium chloride is added to the solution to obtain a final concentration of 41 g/l NaCl.

[0066] After waiting for 30 minutes, the precipitate is collected by decantation through a fabric filter, with a porosity close to 100 microns, then washed 4 times with a 41 g/l solution of NaCl in 0.01 N HCl. This produces 19 kg of acid saline precipitate. This washing process eliminates all traces of periodic acid or iodine derivatives during oxidation of the collagen.

[0067] Then, several washes in an aqueous solution of 80% acetone are used to concentrate the collagen precipitate and eliminate the salts present.

[0068] A final wash in 100% acetone is used to prepare 3.6 kg of a very dense acetone precipitate of acid, oxidized, non-reticulated collagen, with no trace of undesirable chemical products.

[0069] The acetone paste is diluted with apyrogenic distilled water at 40° C., to obtain a 3% concentration of collagen, for a volume of 44 liters. The collagen suspension of a volume of 44 liters is heated for 30 minutes at 50° C., then filtered under sterile conditions through a membrane of 0.45 micron porosity in a drying oven at 40° C.

[0070] As soon as this solution is homogeneous and at 35° C., a sterile concentrated solution of PEG 4000 (polyethylene glycol with a molecular weight of 4000 Daltons) and glycerine is added to it to produce a final concentration of 0.9% PEG, 0.54% glycerine and 2.7% oxidized collagen.

[0071] As soon as these additions have been made, the pH of the solution is adjusted to 7.0 by adding a concentrated solution of sodium hydroxide.

[0072] The collagen solution destined to form the non-porous layer, as described in above, is poured in a thin layer on a flat hydrophobic support such as PVC or polystyrene, at an ambient temperature close to 22° C. A continuous pocket, or channel, or a plurality of longitudinally spaced pockets, or channels, are machined into the surface of the hydrophobic support. The pockets, or channels, in the support correspond to slots or openings in the anvil and/or staple cartridge. The number, dimension and spatial relationship of the pockets, or channels, are determined so as to provide a molded buttress which in turn provides a releasable pressure fit with the slots or openings provided in the anvil or staple cartridge when placed in cooperation therewith.

[0073] The porous layer, prepared as described above, is applied uniformly to the solution of heated collagen, 5 to 20 minutes after it was poured onto the support. This waiting time is the collagen solution gelling time, required for application of the porous layer, to prevent it dissolving or becoming partially hydrated in the liquid collagen.

[0074] Penetration of the porous layer into the gelled collagen solution can be less than 0.5 mm.

[0075] The buttress material is then dehydrated in a jet of sterile air, at ambient temperature, which leads to evaporation in about 18 hours.

[0076] The multilayer buttress material obtained is easy to remove from the support and can be cut to the dimensions required for the application concerned, without weakening it.

[0077] The multilayer buttress material is then put into an airtight double polyethylene bag.

[0078] The unit is sterilized by gamma irradiation or electron beam (beta) irradiation at a dose of between 25 and 35 KGy.

[0079] The material is stable at ambient temperature.

[0080] The collagen solution destined to form the non-porous layer, as described above in EXAMPLE 1, is poured in a thin layer equal to about 0.106 g/cm² on a flat hydrophobic support such as PVC or polystyrene, at an ambient temperature close to 22° C. Several protrusions are machined onto the surface of the mold. The protrusions on the mold correspond to the pins located on the anvil and/or staple cartridge. The number, dimension and spatial relationship of the protrusions, are determined so as to provide a molded buttress which in turn provides a releasable pressure fit with the pins provided on the anvil or staple cartridge when placed in cooperation therewith.

[0081] The remaining collagen solution is diluted with ethyl alcohol and water to produce a final concentration of 1.75% of oxidized collagen.

[0082] Using the diluted solution of 1.75% oxidized collagen, a second layer equal to about 0.041 g/cm² is poured over the first layer, 1 hour or more after the spreading of the first layer.

[0083] Immediately, a surgical mesh reinforcement member is applied on the second layer of the diluted oxidized collagen. The reinforcement member is a knitted isoelastic, multifilament polyglycolic acid mesh which may be completely encapsulated by the second layer of oxidized collagen.

[0084] After 1 hour or more, the porous layer, prepared as described above in EXAMPLE 1, is applied to the mesh.

[0085] The multilayer, reinforced buttress material is dried in a drying cabinet at about 20° C. and about 40% humidity with a horizontal air flow velocity of 1.2 m²/s. The air is blown from the right side of the cabinet to the left side of the cabinet and the incoming air is 0.2 μm filtered and adjusted to 40% humidity. The duration of the drying cycle is between 12 and 24 hours.

[0086] The collagen solution destined to form the non-porous, as described above in EXAMPLE 1, is poured in a thin layer equal to about 0.106 g/cm² on a flat hydrophobic support such as PVC or polystyrene, at an ambient temperature close to 22° C. The remaining collagen solution is diluted with ethyl alcohol and water to produce a final concentration of 1.75% of oxidized collagen.

[0087] Using the diluted solution of 1.75% oxidized collagen, a second layer equal to about 0.041 g/cm² is poured over the first layer, 1 hour or more after the spreading of the first layer.

[0088] Immediately, a surgical mesh reinforcement member, is applied on the second layer of the diluted oxidized collagen. The reinforcement member is a knitted isoelastic, multifilament polyglycolic acid mesh which may be positioned on top of the second layer of oxidized collagen.

[0089] After 1 hour or more, the porous layer, prepared as described above in EXAMPLE 1, is applied to the mesh.

[0090] The multilayer, reinforced buttress material is dried in a drying cabinet at about 20° C. and about 40% humidity with a horizontal air flow velocity of 1.2 m²/s. The air is blown from the right side of the cabinet to the left side of the cabinet and the incoming air is 0.2 μm filtered and adjusted to 40% humidity. The duration of the drying cycle is between 12 and 24 hours.

[0091] The multilayer buttress of EXAMPLES 1-3 are applied to the staple cartridge and/or anvil of a surgical stapler, with the non-porous side in contact with the surface of the cartridge and/or anvil. The edges of a wound are approximated between the staple cartridge and the staple anvil of the stapling apparatus. By firing the stapling apparatus staples are forced out of the staple cartridge and through both the multilayer buttress and, the tissue. The staples are formed by contact with the staple anvil. Once stapled in place the porous layer advantageously reduces bleeding, assists in sealing the wound and allowing tissue ingrowth, if desired, while the non-porous layer provides support for the porous layer and may assist in preventing the formation of adhesions. When present, as in EXAMPLES 2 and 3, the reinforcement member provides additional support to the multilayer buttress and assist in preventing tears during stapling.

[0092] It will be understood that various modifications may be made to the embodiments disclosed herein. Therefore, the above description should not be construed as limiting, but merely as an exemplification of preferred embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the present disclosure. Such modifications and variations are intended to come within the scope of the following claims.