Surgical composite structure having absorbable and nonabsorbable components.

This invention relates to a surgical compos­ite structure. The structure is manufactured from two or more biocompatible polymers. At least one of the polymers in the structure is nonabsorbable.

The nonabsorbable polymer is extruded into a fiber. The fiber can be fabricated into a textile structure. The textile structure can be a woven mesh. The nonabsorbable woven mesh is then encapsulated with at least one bioabsorbable polymer.

The nonabsorbable portion of the composite structure acts as a reinforcement material. Ingrowth of natural tissue is enhanced by the controlled degra­dation of the absorbable portion.

The surgical composite structure of this invention is useful in the repair of defects to the abdominal wall of a mammal. The surgical composite structure of this invention may be useful in preventing hernia formation; and specifically in preventing hernia formation in an infected area.

A surgical composite structure for mammalian tissue has been invented. The composite structure comprises: <ul id="ul0001" list-style="none"><li>a) a nonabsorbable reinforcing component prepared from one or more fibers, at least one of the fibers manufactured from a polymer selected from the group con­sisting of a fiber forming fluoropolymer, polybutester, polyester, polyamide, poly­olefin, and blends of the same, and</li><li>b) a bioabsorbable component comprising a polymer prepared from one or more monomers selected from the group consisting of lactides, carbonates, oxalates and lactones.</li></ul> In one embodiment, the nonabsorbable component is selected from the group consisting of a fiber forming fluoropolymer, a polybutester, and a polyester.

In another embodiment, the bioabsorbable component comprises a polymer prepared from one or more monomers selected from the group consisting of lactides, carbonates and lactones. In a specific embodiment the lactides are selected from the group consisting of glycolide and 3,6-dimethyl-2,5-p-­dioxanedione; the carbonate is 1,3-dioxan-2-one; and the lactones are ε-caprolactone and 1,4-dioxan-2-one. In another specific embodiment, the bioabsorbable component is selected from the group consisting of lactides and carbonates.

In yet another embodiment, the nonabsorbable component is in the form of a sheet. In a specific embodiment, the bioabsorbable component is laminated to at least one side of the sheet. In a more specific embodiment, the bioabsorbable component is laminated to both sides of the sheet. In another specific embodi­ment, the nonabsorbable component is in the form of a knitted, woven, flat braided, or nonwoven sheet. In a preferred embodiment, the nonabsorbable component is in the form of a woven sheet.

An alternative surgical composite structure for mammalian tissue has been invented. The alterna­tive structure comprises: <ul id="ul0002" list-style="none"><li>a) a nonabsorbable reinforcing component prepared from a plurality of fibers, at least one of the fibers manufactured from a polymer selected from the group con­sisting of a fiber forming fluoropolymer, a polybutester, a polyester, and blends of the same, and</li><li>b) a bioabsorbable component comprising a polymer prepared from one or more mono­mers selected from the group consisting of lactides, carbonates and lactones.</li></ul> In one embodiment the lactides are selected from the group consisting of glycolide and 3,6-dimethyl-2,5-p-­dioxanedione; the carbonate is 1,3-dioxan-2-one; and the lactones are selected from the group consisting of ε-caprolactone and 1,4-dioxan-2-one.

In a specific embodiment, the bioabsorbable component is manufactured from the monomers glycolide and 1,3-dioxan-2-one. In another specific embodiment, the nonabsorbable component is in the form of a knitted or woven sheet.

Another alternative surgical composite structure for mammalian tissue has been invented. The structure comprises: <ul id="ul0003" list-style="none"><li>a) a nonabsorbable woven component prepared from a plurality of fibers, the fibers comprising a polymer selected from the group consisting of polytetrafluoro­ethylene, a copolymer of tetrafluoro­ethylene and hexafluoropropylene, per­fluoroalkoxy resin, ethylene-chlorotri­fluoroethylene copolymer, ethylene-terta­fluoroethylene copolymer, and polyvinyl­idene fluoride, and</li><li>b) a bioabsorbable component laminated to the nonabsorbable woven component, the bioabsorbable component comprising a polymer prepared from at least two monomers selected from the group consist­ing of lactides, carbonates and lactones.</li></ul>

In one embodiment, the nonabsorbable woven component is selected from the group consisting of polytetrafluoro­ethylene, a copolymer of tetrafluoroethylene and hexa­fluoropropylene, and polyvinylidene fluoride. In a specific embodiment, the nonabsorbable woven component consists of a copolymer of tetrafluoroethylene and hexafluoropropylene.

In another specific embodiment, the bioabsorbable component comprises a random copolymer. In a more specific embodiment, the random copolymer is prepared from at least the monomers glycolide and 1,3-dioxan-2-one.

Yet another alternative surgical composite structure for mammalian tissue has been invented. The structure comprises: <ul id="ul0004" list-style="none"><li>a) a nonabsorbable woven component prepared from a plurality of fibers, the fibers comprising a polymer selected from the group consisting of a polybutester and polybutylene terephthalate, and</li><li>b) a bioabsorbable component laminated to the nonabsorbable woven component, the bioabsorbable component comprising a polymer prepared from at least two monomers selected from the group consist­ing of lactides, carbonates and lactones.</li></ul> In a specific embodiment, the nonabsorbable woven component is a polybutester.

In another specific embodiment, the bioabsorbable component comprises a random copolymer. In a more specific embodiment, the random copolymer is prepared from at least the monomers glycolide and 1,3-dioxan-2-one.

A drawing which describes the shape and/or geometrical configuration of the surgical composite structure is not necessary for an understanding of this invention. That is, any person skilled in the surgical composite structure art will know how to manufacture and how to use the invention by reading this specifica­tion, generally and the examples, specifically.

It is to be understood that the bioabsorbable component can be coated onto the nonabsorbable rein­forcing component by any coating means known in the prior art. The inventors have found that lamination is an adequate means for coating. Specifically, the inventors have found that bonding the bioabsorbable component to the nonabsorbable reinforcing component by fusion is an adequate means of laminating the two components. However, other forms of coating, such as encapsulation, are within the scope of this invention.

Throughout this disclosure, it is to be understood that the term Teflon is a trademark of the E. I. DuPont and Company, DE, U.S.A., whether the term Teflon is or is not so identified as a trademark.

The term fluoropolymer is generic and in­cludes the terms fluoroplastic and fluoroelastomer.

The Teflon™ FEP described in the examples is a copolymer of tetrafluoroethylene and hexafluoro­propylene. It is also to be understood that the term polybutester as used in this disclosure is synonymous with the terms polyetherester, polyether-ester or polyether ester. A commercially available polybutester is the Hytrel™ (E. I. DuPont and Co.) copolymer.

Preferred embodiments of this invention are more fully described in the Examples 1 to 6, below.

COMPARATIVE EXAMPLE A

A woven mesh, identified as Style T-151-56 and supplied by Stern &amp; Stern Textiles, Inc., Hugnet Fabrics Div., Hornell, NY 14843, U.S.A. is used as a control for the composite meshes of Examples 1 and 2, below. It is made with monofilament fibers of Teflon™ FEP (E. I. DuPont and Co.) polymer with a diameter of 5 to 6 mils (or 0.005 inch to 0.006 inch). These fibers are woven into a mesh configuration of approximately 80 x 90 strands per inch. The overall thickness of the woven fabric is approximately 12 mils (or 0.012 inch).

EXAMPLE 1

A composite structure consisting of a fabric of a woven mesh made up of biocompatible, nonabsorb­able, monofilament fibers is encapsulated by lamination between two films of a bioabsorbable polymer. The woven mesh is described in Comparative Example A, above.

The films of bioabsorbable polymer used in the laminated composite are prepared by compression molding a random copolymer of 50/50 weight per cent of glycolide trimethylene carbonate to a thickness of approximately 10 mils (or 0.010 inch) thick. The manufacture of the random copolymer is described, without the need for undue experimentation, in the prior art.

The conditions for molding these films is as follows. A pre-dried, preformed pellet of approxi­mately 5.0 grams of the copolymer is placed between two 7 inch x 7 inch caul plates and Teflon PTFE release film. This assembly is placed in a 6 inch x 6 inch press which is pre-heated to 145°C ± 5°C and gradually increased in pressure to 1,000 lbs. force on a 1 3/4 inch diameter ram. The pressure is held constant for 3 minutes. Subsequently, this assembly is removed from the press, and cooled to approximately 15°C under pressure. The film is then easily released from between the Teflon release film. The resultant film is a transparent, amber-colored film of approximately 10 mils (0.010 inch) thick x 5 inches x 5 inches.

The final composite structure is formed by laminating a film of the copolymer on either side of the Teflon FEP woven mesh between two 7 inch x 7 inch caul plates and Teflon PTFE release film. This assem­bly is placed in a 6 inch x 6 inch press which is pre-heated to 145°C ± 5°C and gradually increased in pressure to 1,000 lbs. force. The pressure is held constant for approximately 3 minutes. Subsequently, this assembly is removed from the press and cooled to approximately 15°C under pressure. The laminated composite structure is then easily released from between the Teflon PTFE release film. the resultant laminated composite consists of a Teflon FEP woven fabric which is completely encapsulated within the fused copolymer of 50/50 weight percent poly­(glycolide-co-trimethylene carbonate). The resultant laminated composite is approximately 20 mils (0.020 inch) thick and 5 inches x 5 inches in size.

EXAMPLE 2

A composite laminated structure is prepared similar to that described in Example 1 except the polymer films are made with a random copolymer of 68/32 weight per cent of glycolide trimethylene carbonate substituted for the 50/50 weight per cent copolymer. Also, the processing temperature was increased to approximately 150°C ± 5°C.

The preparation of the random copolymer is described, without the need for undue experimentation, in the prior art.

EXAMPLE 3

A composite laminated structure is prepared similar to that described in Example 2 except that the woven mesh is made from monofilament fibers of HYTREL® with a diameter of 5 to 6 mils (0.005 inch to 0.006 inch). Hytrel™ (E. I. DuPont and Co.) is a polyether-ester, and can be a polymer of polytetramethylene glycol with terephthalic acid and 1,4 - butanediol. These fibers are woven into a mesh configuration of approximately 80 x 90 strands per inch. The overall thickness of the woven fabric is approximately 12 mils (0.012 inch).

EXAMPLE 4

Sterile, composite structure samples of the type described in Example 1 were implanted in 3 rats to determine the initial efficacy of this composite structure.

At 6 weeks following implantation the compos­ite structure seemed to be associated with much inflam­mation. At 6 months this did not appear to be the case, and the Teflon FEP mesh component of the compos­ite structure was well-encased in the animal subcutane­ous tissues.

EXAMPLE 5

Sterile, composite structure samples of the type described in Comparative Example A and Example 1 were implanted in 36 rats. Each wound area was infect­ed by the introduction of staphylococcus aureus, E. coli, and bacteriodes in a mixture of 10⁵ organisms per milliliter.

Thirty-two of the 36 rats implanted with the uncoated Teflon FEP woven mesh of Comparative Example A showed clinical signs of infection. All of these results were confirmed histologically. Many white cells were found around the abscess cavity. These were cultured positive for mixtures of organisms which were implanted during the operative placement of the Compar­ative Example A uncoated Teflon FEP woven mesh.

After 6 months implantation the results indicated that 35 out of the 36 rats were free of infection with implants of the composite structure of Example 1.

EXAMPLE 6

An additional <u style="single">in vivo</u> study was conducted to confirm the advantages of a tissue reinforcing woven mesh made from fibers of a nonabsorbable polymer encapsulated or coated with an absorbable polymer, versus an uncoated mesh, in an infected wound area.

Both sterile, composite structure samples of the type described in Example 2 and uncoated Teflon FEP woven mesh samples described in Comparative Example A were implanted in 18 rabbits. Each animal was implant­ed with two (2) samples of coated mesh and two (2) samples of uncoated mesh diagonally on shoulder/hip quadrants. Each wound area was infected as described in Example 5, above.

The results of this study indicated that there was no infection in the areas of the composite structure samples at the end of 6 weeks. In the uncoated Teflon FEP woven mesh wounds all were found to be infected after 6 weeks.