WO1998014134A2

WO1998014134A2 - Knitted surgical mesh

Info

Publication number: WO1998014134A2
Application number: PCT/US1997/017987
Authority: WO
Inventors: Margaret M. D'aversa; Robert Dougherty
Original assignee: Ethicon, Inc.; Prodesco, Inc.
Priority date: 1996-10-04
Filing date: 1997-10-03
Publication date: 1998-04-09
Also published as: WO1998014134A3

Abstract

This invention is a knitted surgical mesh (10) formed from a yarn. The knitted mesh has from 11 courses per inch to 13 courses per inch, and from 8 wales per inch to 10 wales per inch, a flexibility of from 10 gfcm/cm to 16 gfcm/cm, a burst strength greater than 175 pounds per square inch, and a pore size percentage greater than 37 %.

Description

KNITTED SURGICAL MESH

Field of the Invention

This invention relates to a textile material and, in particular, to a surgical mesh of

knit construction fabricated from a polypropylene monofilament yarn.

Background

Hernia repairs are among the more common surgical operations which may

employ a mesh fabric prosthesis. Such mesh fabric prostheses are also used in other

surgical procedures including the repair of anatomical defects of the abdominal wall,

diaphragm, and chest wall, correction of defects in the genitourinary system, and repair

of traumatically damaged organs such as the spleen, liver or kidney.

Mesh fabrics for use in connection with hernia repairs are disclosed in U.S. Patent

Nos. 5,292,328, 4,769,038 and 2,671,444. Knitted and woven fabrics constructed from a

variety of synthetic fibers and the use of the fabrics in surgical repair are also discussed

in U.S. Patent Nos. 3,054,406; 3,124,136; 4,193,137; 4,347,847; 4,452,245; 4,520,821 ;

4,633,873; 4,652,264; 4,655,221 ; 4,838,884;. 5,002,551 ; and European Patent

Application No. 334,046.

It is desirable for a surgical mesh fabric prosthesis to exhibit certain properties

and characteristics. In particular, the mesh should have a burst strength sufficient to

ensure that the mesh does not break or tear after insertion into a patient. The mesh

should also have a pore size which allows tissue to penetrate or "grow through" the mesh, after the mesh has been inserted into a patient. In addition, the mesh should be

constructed so as to maximize its flexibility, thereby facilitating the insertion of the mesh

prosthesis into a patient during a surgical operation.

It is an object of the present invention to provided a knitted surgical mesh having

a high burst strength and large pore size, which has a greater flexibility than known

knitted surgical mesh fabrics.

These and other objects and advantages of the invention will become more fully

apparent from the description and claims which follow or may be learned by the practice

of the invention.

Summary Of The Invention

The present invention is directed to a knitted surgical mesh formed from a yarn.

The knitted mesh has from 11 to 13 courses per inch and from 8 to 10 wales per inch, a

flexibility of from 10 to 16 gfcm/cm, a burst strength greater than 175 pounds per square

inch, and a pore size percentage greater than 37%.

Brief Description Of The Drawings

In order that the manner in which the above-recited and other advantages and

objects of the invention are obtained and can be appreciated, a more particular

description of the invention briefly described above will be rendered by reference to a

specific embodiment thereof which is illustrated in the appended drawings.

Understanding that these drawings depict only a typical embodiment of the invention and

are not therefore to be considered limiting of its scope, the invention and the presently

understood best mode thereof will be described and explained with additional specificity

and detail through the use of the accompanying drawings.

Figure 1 is a diagram showing a knitted surgical mesh, in accordance with a

preferred embodiment of the present invention.

Figure 2 is an enlarged view of a portion of the surgical mesh shown in Figure 1.

Description Of The Preferred Embodiments

The surgical mesh of this invention is preferably fabricated from a yarn which is

already accepted for use as a suture material. In a preferred embodiment, the surgical

mesh is fabricated from a monofilament yarn formed from a polypropylene resin, such as

that disclosed in U.S. Patent No. 4, 911,165, entitled "Pliablized Polypropylene Surgical

Filaments" and assigned to Ethicon, Inc., the contents of which is hereby incorporated in

its entirety by reference. The preferred monofilament polypropylene yarn used has a

denier of from about 30 to 300, and more preferably a denier of about 141. Alternatively, a multifilament yarn, such as a multifilament polypropylene yarn may be

used to fabricate a surgical mesh in accordance with the present invention. In still further

alternate embodiments, the yarn used to form the mesh may be formed from silk, linen,

cotton, nylon, polyester (i.e., polyethelene terathalate, polybutulene terathalate, and

mixtures thereof), polyethylene, stainless steel, hydrolytic polymers, such as those which

may derived from lactone monomers, including but not limited to glycolide and lactide

(including acid forms thereof), 1 ,4 dioxin, trimethylene carbonate, Δ-valero lactone, ε-

caprolactone, 1,4 dioxepan-2-1, 1 ,5 dioxepan-2-1 , and alkyl substituted equivalents of

these compounds, as well as the cyclic dimers of these compounds.

The surgical mesh of this invention is preferably fabricated from a 141 denier

monofilament polypropylene yarn by employing known and conventional warp knitting

apparatus and techniques, such as the tricot and Raschel knitting machines and

procedures described in "Warp Knitting Production" by Dr. S. Raz, Melliand

Textilberichte GmbH, Rohrbacher Str. 76, D-6900 Heidelberg, Germany ( 1987), the

contents of which are incorporated by reference herein. As is well known in the art of

warp knitting, the number of courses and wales per inch in a knitted material is affected

by a number of machine operating variables such as the rate at which the fabric is drawn

away from the needles, the number of needles per inch, the amount of tension applied to

the warp yarns and other variables after the fabric leaves the machine, e.g., the heat

setting conditions. In the preferred embodiment of the present invention, the preferred

polypropylene monofilament yarn described above is warp knitted, preferably tricot

knitted on a 2 bar set-up, in accordance with the parameters set forth in Table I below: TABLE I

Courses per Inch Wales per Inch Back Bar Front Bar

11-13 8-10 2/3 1/2

1/0 1/0

Following knitting, the mesh is cleaned or scoured, and thereafter annealed to

stabilize the fabric. For the latter operation, the mesh can be secured to a tenter frame

which maintains the mesh at a predetermined width, the frame then being passed through

an elongate heating zone at a temperature of from about 100° to about 160° C, preferably

at a temperature of from about 120° to about 150° C, at a rate providing a dwell time of

from about 1 to about 60 minutes and preferably from about 5 to about 25 minutes.

Following heat setting, the mesh is cut to size, packaged and sterilized.

The mesh can be cut to any desired configuration, e.g.. a square or rectangular

shape, of appropriate dimensions. A preferred configuration 10 having a key-hole

opening 20 is shown in Fig. 1. An ultrasonic slitter may be employed to cut the mesh,

various types of which are commercially available. Unlike the result one obtains when

cutting with a blade, i.e., frayed yam ends, or when the yam ends are heat-sealed, i.e.,

bead-like formations, cutting the mesh to size with an ultrasonic cutter avoids both

frayed and beaded ends.

The polypropylene monofilament knitted mesh fabricated as described above

exhibits high flexibility. Depending on the yam used to form the mesh, a mesh formed in accordance with Table I above preferably has a flexibility of about 10 to 16 gram-

force-cm/cm and, when the 141 denier monofilament yam described above is used, the

mesh has a flexibility of 14.7 gfcm/cm. In addition, depending on the yam used to form

the mesh, a mesh formed in accordance with Table I above preferably has a burst

strength of about 175-250 pounds per square inch and, when the 141 denier

monofilament yam described above is used, the mesh has a mean burst strength of 223

pounds per square inch which varies between about 210 to 234 pounds per square inch

depending on the sample. Finally, depending on the yarn used to form the mesh, a mesh

formed in accordance with Table I above preferably has a pore size percentage of from

about 37% to 50%. and, when the 141 denier monofilament yam described above is used,

the mesh has a pore size of about 42%. The polypropylene monofilament knitted mesh

fabricated as described above preferably possesses a thickness of from 20 to 30 mils

depending on the particular yam used, and, when the 141 denier monofilament yam

described above is used, the mesh has a mean thickness of 24.7 mils which varies

between about 24 to 25 mils depending on the sample. The flexibility, burst strength and

pore size characteristics for a mesh fabric fabricated as described above and other meshes

that are currently commercially available are compared in Table II set forth below:

TABLE II

Mesh Fabric Flexibility Burst Strength Pore Size Thickness (gf cm/cm) (PSI) (%) (Mils)

Present Invention 14.73 223 42.0 24.7

Marlex Mesh (mfd. by 14.86 148 31.71 25.9 CR. Bard)

Prolene Mesh (mfd. by 18.92 241 49.73 29.0 Ethicon, Inc.) As shown in Table II, the mesh of the present invention has: (i) a significantly

better flexibility than the Prolene mesh fabric, and (ii) a significantly higher burst

strength and pore size percentage than the Marlex mesh fabric. The mesh of the present

invention thus achieves a flexibility which is slightly better than the Marlex mesh

material while, at the same time, exhibiting burst strength and pore size characteristics

which are comparable to the less-flexible Prolene material.

Furthermore, it is to be understood that although the present invention has been

described with reference to a preferred embodiment, various modifications, known to

those skilled in the art, may be made to the structures and process steps presented herein

without departing from the invention as recited in the several claims appended hereto.

Claims

What is claimed is:

1. A knitted surgical mesh comprised of a knitted yarn, the knitted mesh having

from 1 1 to about 13 courses per inch and from 8 to 10 wales per inch, a flexibility of

from 10 to 16 gfcm cm, a burst strength greater than 175 pounds per square inch, and a

pore size percentage greater than 37 %.

2. The knitted surgical mesh of claim 1 , wherein the pore size percentage of the

mesh is from 37 % to 50 %.

3. The knitted surgical mesh of claim 2, wherein the pore size percentage of the

mesh is 42%.

4. The knitted surgical mesh of claim 1, wherein the mesh has a burst strength

from 210 to 234 pounds per square inch.

5. The knitted surgical mesh of claim 1, wherein the mesh has a thickness of

from 20 to 30 mils.

6. The knitted surgical mesh of claim 5, wherein the thickness of the mesh is

from 24 to 25 mils.

7. The surgical mesh of claim 1, wherein the yam is a polypropylene yarn.

8. The surgical mesh of claim 7, wherein the ya is a monofilament

polypropylene yarn.

9. The surgical mesh of claim 8, wherein the yarn has a denier of from 30 to 300.

10. The surgical mesh of claim 1, wherein the mesh includes a key-hole shaped

opening within an interior region of the mesh.