Flat implant, process for its production and use in surgery

Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Having means to promote cellular attachment

Reexamination Certificate

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C606S213000

Reexamination Certificate

active

06447551

ABSTRACT:

DESCRIPTION
The present invention relates to a flat implant, a process for its production and its use in surgery.
Hernia is a frequently encountered illness. It generally consists of a passage of organs or organ parts out of the natural body cavity through a preformed or acquired gap. Among external hernias, where the hernial sac is always surrounded by the peritoneum, the most frequently encountered forms are groin, umbilical and incisional hernias. The reason for hernias occurring are in particular muscle or connective tissue weaknesses in conjunction with overstressing, age-caused atonia, congenital weakness of the abdominal wall or inadequate cicatrization following a body section (incisional hernia).
In most cases effective treatment by surgery is possible, where the hernia content is transferred back from the hernial sac into the abdomen and the hernial opening is closed. This closure of the hernial opening normally takes place by a suture.
However, this surgical procedure suffers from the disadvantage that in up to 20% of cases a further hernia occurs, i.e. the so-called hernial relapse.
Due to this unsatisfactory relapse rate following conventional hernia operations, in modern hernia surgery increasing use is being made of artificial strengthening materials for the reconstruction of the abdominal wall. Polypropylene and also polyester nets play an important part.
Although the use of such nets has clearly led to a marked decrease in the relapse rate, such implants are not unproblematical due to possible infections or fistula formations and in particular due to the soft tissue adhesion risk.
The hitherto known implants consist of open textile structures, which aid an adhesion of cells and also a growing through of cells. This is advantageous, because it forms a firm connection between the implant and the abdominal wall and thus ensures the desired support function. However, it can lead to difficultly removable cicatrizations in the abdominal cavity with hardening effects, detrimental action on the intestine and internal organs and the associated complaints on the part of the patient.
Flat, textile implants are also known, which are sealed with an impregnating agent. However, problems then arise in fixing to the abdominal wall, particularly when spending a long time in the body.
The problem is to make available an implant for use in surgery, which overcomes the difficulties of prior art implants, which is easy and inexpensive to manufacture and which is usable by employing conventional surgical methods.
Accordingly, it is an object of this invention to provide a flat implant comprising a flexible fabric comprising two sides and having on one side a substantially closed surface and on the other side a three-dimensional microstructure permitting a growing in of cells, wherein the substantially closed surface comprises micropores, wherein the micropores permit an exchange of materials and are sufficiently small to prevent the growing in of cells, the closed surface being formed by a surface layer connected to the flexible fabric as a coating formed by spray coating of a web of a polymer, and the three-dimensional microstructure having back-engagement points for the growing in of cells formed by at least one of a woven fabric and a knitted fabric, the implant having an air permeability of 5 to 100 ml of air/cm
2
.min at a pressure difference of 1.2 kpascal. The implant according to the invention permits a good anchoring of body cells on the structured side facing the abdominal wall and prevents an undesired cicatrization with organs and body parts on the substantially closed side facing the abdominal cavity. It is another object of this invention to provide a method for the production of the implant by forming a unilaterally closed surface on one side of a porous, particularly textile fabric for preventing the growing in of cells.
For use in surgery the invention provides a flat implant to be used with a flexible fabric, which has on one side a substantially closed surface and on the other side a three-dimensional microstructure permitting the growing in of cells. In particular, the substantially closed surface can be microporous, the micropores being so small that they allow an exchange of material, but substantially prevent the growing in of cells.
Preferably the substantially closed surface is smooth. The substantially closed surface can also be formed by a surface layer connected to the flexible fabric, particularly a coating of said fabric.
According to the invention, the three-dimensional microstructure can have back-engageable points for the growing in of cells. Advantageously the flexible fabric is formed by a porous, flexible structural material, particularly a flexible support and the three-dimensional microstructure is formed by the exposed surface structure of the structural material. Examples of porous, flexible structural materials are open-cell structural foam or a lattice structure.
Advantageously the implant is formed by at least one synthetic polymer material. Preferably the fabric of the implant according to the invention is formed from polypropylene, polyester, polytetrafluoroethylene and/or polyester and polytetrafluoroethylene. Particular preference is given according to the invention to a flat polyester and polytetrafluoroethylene implant. It is also possible to use resorbable materials such as polylactides, polyglycolides and copolymers thereof, if a resorbability or partial resorbability is desired.
In an embodiment of the invention the flexible structural material can be a textile material, particularly a porous textile support. Preferably the flexible textile support at least on the side with the three-dimensional microstructure has an open textile structure known in connection with vascular implants and which is in particular formed by textured yarns, float stitches and/or velours loops, such as are e.g. known from U.S. Pat. No. 4,047,252, U.S. Pat. No. 3,878,565, DE 2,461,370 and U.S. Pat. No. 4,517,687.
It is possible to process shrinkable fibers and yarns produced therefrom such as other fibers and yarns using conventional procedures so as to give textile fabrics. Subsequently as a result of shrinkage treatment the shrinkable fibers are shrunk, which in the case of the textile fabric produced therefrom leads to a compression of the structure. As a result of the planned use of shrinkable fibers and non-shrinkable fibers in the combination, it is possible in planned manner to effect modifications to the textile structure.
It is possible to process shrinkable fibres and yarns produced therefrom such as other fibres and yarns using conventional procedures so as to give textile fabrics. Subsequently as a result of a shrinkage treatment the shrinkable fibres are shrunk, which in the case of the textile fabric produced therefrom leads to a compression of the structure. As a result of the planned use of shrinkable fibres and non-shrinkable fibres in combination, it is possible in planned manner to effect modifications to the textile structure.
According to the invention the fabric can be produced according to a textile method, particularly knitting, weaving or braiding. Such procedures are known to the expert, so that there is no need for a detailed explanation here. This permits a simple, inexpensive manufacture according to known, proven procedures and using conventional machines and tools.
Advantageously the flexible textile fabric, particularly the textile support, can be a woven fabric or in particular a knitted fabric, which at least on the three-dimensionally structured side has exposed fibres or threads serving to anchor the cells.
It is possible to use textile fibrous materials such as synthetic monofilaments, multifilament threads or multifilament yarns. Preferably, according to the invention, the fabric can at least partly be formed from multifilament yarns, which can be smooth or structured. In an embodiment of the invention the yarns can be formed from a single fibrous material type. In another embodiment the yarns can be formed from sever

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