US3187752A - Non-absorbable silicone coated sutures and method of making - Google Patents

Description

June 8, 1965 A. GLICK 3,187,752

NON-ABSORBABLE SILICONE COATED SUTURES AND METHOD OF MAKING Filed April 27, 1962 j z INVEI qTOR.

ARTHUR GL ICK BY M Wmm United States Patent 0 3,187,752 NUN-ABSORBABLE SILICGNE COATED SUTURES AND METHGD 0F MAKDIG Arthur Gliclr, Danbury, Count, assignor to American 1(Iqyanamid Company, Stamford, Conn., a corporation of ame Filed Apr. 27, 1962, Ser. No. 199,604 26 Claims. (Cl. 128--335.5)

This application is a continuation-in-part of application Serial Number 767,502, filed October 16, 1958 and now abandoned.

This invention relates to a non-absorbable densely constructed suture built up of a plurality of filaments 113V, ing a serum-proof, moisture-resistant coating on the surface of the individual filaments, which coating contains a silicone resin.

As used in this specification the term suture is intended to include both sutures, as are used for the sewing of tissues, and ligatures as used for tying off blood vessels, etc. Different portions of one strand may be used for both purposes in the same operation depending upon the needs of the surgeon at the particular moment.

In surgical practice; and for present purposes, this includes both human and animal surgery, two classes of sutures are commonly used. One is the absorbable suture which is absorbed by the tissues and accordingly loses its identity, such sutures usually being of catgut, etc.; and the other form is a non-absorbable suture which in most instances is permitted to remain as such pen strong and should maintain their strength and integrity for prolonged periods while in contact with body tissues and fluids. It is desirable that such sutures be inert, causing a minimum of tissue irritation, and that the diffusion of fluids through the suture by capillarity be at a minimum. 1

It has been customary to use silk sutures built up as by braiding, Weaving, twisting or spinning, hereafter called coordinate configuration, of from a plurality of individual silk filaments. Synthetic polymers may be used instead of natural silk. These filaments present a construction in which there are fine interstices which by capillary action cause fluids to travel along the length of the suture. This may permit migration of pathogenic organisms.

Accordingly, such sutures have been coated with waxes, such as beeswax, or beeswax mixed with ethyl cellulose, which material reduces the capillarity of the suture and improves the handling characteristics of the suture.

There is some evidence that under some conditions these waxes cause granuloma formation, and have other undesirable side ellects.

Additionally the coating material should be inert to all body fluids and heat stable to permit heat sterilization of the suture. It is desirable that the coating be economical and readily applied.

In addition to the physiological properties of inertness the characteristics of handling and of strength of a suture are extremely important. It is desirable that a suture be sufiiciently still that it can be easily handled and yet readily formable to a new position. After being bent to a new position, it should maintain this new set position. Many fibrous materials have a plastic memory, and after being bent to a new position slowly on standing tend to go back to their former shape. A suture should not have plastic memory but should when once set maintain that new position.

Additionally the suture should be easy to tie in a knot and should be resistant to knot-slippage under strain and the knot should remain secure and not slip or untie itself on standing. Additionally, a suture should have what is known as throwability. That is, the surgeon should be able to pick up the suture and throw it to a new position, which position is then retained. It is desirable at' times to place a suture in a given location or throw it in a given direction with the knowledge that the suture will stay there until-positively moved.

In the past a great deal of the handling characteristics have been imparted to a limp suture by the coating material. Beeswax or beeswax mixed with ethyl cellulose used as a coating is responsible for the desirable handling characteristics.

If some other coating material is used with the same filament construction, the sutures may not have satisfactory handling characteristics.

it has now been found that by braiding a suture with a tighter and more dense construction using fewer picks, i.e. cross-overs per inch, and by dry stretching the braided filaments, a suture can be formed which has inherently stiffer qualities and improved handleability.

Silk is the usual material used for non-absorbable sutures. Synthetic filaments such as nylon, polypropylene, Or-lon, polyacrylonitrile, Dacron, a stretched oriented polyester of ethylene glycol and terephthalic acid, etc., or cotton, or linen are sometimes used. Occasionally such materials as stainless steel or horsehair are used. All such materials can be advantageously coated with polymeric silicones, in accordance with this invention, and are braided or spun or formed more tightly for coating with silicones than with conventional coating materials.

Polymeric silicones are applied to this denser suture; such polymeric silicones readily coat the individual filaments increasing the resistance to aqueous fluids thus a reducing capillarity. Furthermore, such silicones applied'as a coating are heat stable. In at least some instances the coating may be applied in a partially polymerized state and the silicone further polymerized in position on the suture. Fortunately and fortuitously, polymerization catalysts are decomposed by heat sterilization procedures or heat curing so that even if toxic catalysts are used as a component of the silicone coating, the final product is completely inert.

The particular silicone resins themselves are not a part of this invention and standard commercial resins may be used. It is not necessary that the material be applied as a liquid, as some of these silicone resin forming materials, such as the General Electric Drifilrns, are volatile and may be applied in the gaseousphase. These materials are among the volatile silicone compounds such as alkyl silicone halides. A material such as dimethyl silicone dichloride is comparatively volatile and may be applied either direct or by allowing an ethereal solution thereof to evaporate and the vapors contact the suture material.

Frequently, it is more convenient to use a liquid preparation. Such preparations are solvent dispersions of silicone resins, that is partially olymerized products which will polymerize to a silicone film. For purposes of convenience it is normally easier to purchase the material under trade-names rather than making it, or obtain it to a performance specification. Materials which are sold commercially such as the Dow-Corning silicone DC DC 804 or General Electrics 9980 give highly satisfactory and useful films. To those skilled in the art of silicone compounding it is comparatively simple to select a heat-curable or potentially heat-curable silicone resin, which either from its inherentcharacteristics, or

s eaves :3 the addition of a polymerizing catalyst, will set up or cure. As a final check to insure the complete removal oi all halide to silicone linkages, ammonia fumes may be used. Usually sufiicient moisture is present to insure the hydrolysis of the halogen, but ammonia fumes insure a neutral product. I desired, silicone containing resins may be used in which the silicone atoms are linked through nitrogen, from ammonia, rather than through oxygen as in the silicones, such resins at times being referred to as silamines.

Methods for preparation of silicone resins are well known. Patent No. 2,306,222 to W. I. Patnode, Method of Rendering Materials Water Repellant, discloses the use of a vapor of an alkyl silicone halide for making glass vapor-proof. The same types of materials as therein described may be used to water-proof and treat sutures. The patent to Safford, No. 2,424,853, and the patent to Tanis, No. 2,408,822, additionally describe siliceous halides and their conversion to resins. There are several methods of preparing such silicone resins, among others are the reaction of Grignard type reagents with a silicone tetrahalide. From the standpoint of costs silicone tetrachloride is normally used and the Grignard may be either alkyl or aryl or a mixture thereof. The amounts of alkyl and aryl groups used affect the brittleness and rate of cure of the resin formed. Normally the product of the reaction of the Grignard reagent with silicone tetrachloride is allowed to react with moisture, allowed to partially polymerize, and the partially polymerized materials are dissolved in a suitable solvent whereby additional polymerization is either inhibi ed or substantially slowed down; The higher the ratio of lower alkyls, the more rapid the materials will cure and the more brittle will be the film. The more highly branched the chains formed in the resin, which are necessarily formed by the polymerization of the silicone types containing more halide atoms per silicone molecule, the more brittle and polymerized are the resins.

The organo-silicones sometimes referred to as organopolysiloxanes, more particularly the hydrocarbon substituted polysiloxanes are particularly suitable for suture coating. The patent to Wright et al., No. 2,389,477, entitled Polysiloxane Resins gives considerable information'or" this type of resin. Certain of the resins which are described in the patent to Hyde, No. 2,386,466, Insulated Conductor and Insulation Therefor, it diluted with body fluids. in neural surgery, suture materials frequently deleteriouslyaifect regeneration of nerve fibers. Silicone coated silk is the first material known to have been successfully used in suturing nerve fibers which permits the regeneration of the nerves in the spinal column.

Usually silk is braided loose enough for a beeswax coating to impregnate the silk, reduce capillarity, and impart desirable handling qualities. The new silicone coating may not inherently have enough body to give the desired handling qualities. Rather than use a more highly polymrized' silicone resin, which is stiller, it is preferred to use a denser silk construction, with more silk filaments in a given cross-section. This gives a greater strength, and a thinner silicone coating gives a proper inertness to the suture and at the same time prevents capillarity.

One standard test for capillarity is to boil two 3 to 4 inch lengths of the suture in distilled water in a glass container for three successive 20-minute periods, changing the water each time. After the third boiling, the test sutures are allowed to stand for at least 8 hours in an atmosphere having a relative humidity of 65% 12% at a temperature of 2lil C. The segment of suture is tied to a piece of white silk thread with a square knot, the ends cut close, and suspended by the white silk thread so that the suture dips into a 0.5% aqueous solution of methylene blue, with the knot %-inch above the dye solution. After standing for 24 hours, the white silk is inspected for evidence of dye carried up the suture by capillary action. It the white silk is free from dye color, the suture is non-capillary, and passes the test. Both of the duplicate samples should pass.

Sutures of this invention pass this test for capillarity. Sutures which pass this test'are non-capillary in tissues of man and animals.

For preventing slippage at knots in the suture, a coating forming ahardened, but flexible silicone film ispreferred, using a silicone having a higher ratio of with a solvent may be used in accordance with the instant invention. The patent to Hyde, No. 2,371,050, Organo- Silicone Polymers and Method of Making Them, de-

scribes certain additional methods of preparing such resins. It is not necessary that the resins be prepared from halogen containing compounds as, for example, methods such as set forth by Strain et al. in Patent No. 2,394,642, Silicic Acid Esters, describes a difierent form of silicone containing resin. The patent to Iler, No. 2,395,550, Modified Alkyd Resins, describes still further modifications of silicone containing resins in which the silicone linkages are different than those classified as organo-polysiloxanes.

It is not intended that a treatise be here included on the production of such resins, as such resins are the invention of others and are adequately described in the patent literature, as well aselsewhere. The texts Introduction to the Chemistry of the Silicones, Eugene G.

,closes some of the silicones which may be used, and other medical usages for such silicones.

The silicone acts as a protectivc'layer on the surface of the filaments, and prevents dyes or the surface characteristics of the filaments, suchas silk, from interacting aryl groups. For instance, a polysiloxane having from about 72% to 67% methyl substituents and from 28% to 33% phenyl groups cures to a non-slipping finish that gives excellent knot retention. Usually the suture breaks before the knot slips. Also such polysiloxanes are sufficiently adhesive that spun sutures of silk or other filaments do not unravel, or broom, and can bethreaded into needles. 7

The silk construction itself rather than the coating can beused to give the handling qualities.

Whereas the number of ends, and total denier, varies with size, it is desirable that a maximum size, and

strength be obtained within the overall limits of suture diameter. For the standard United States Pharmacopeia sizes (United States Pharmacopeia Convention, Inc., Distributed by Mack Publishing Co., Easton, Penn., elsewhere abbreviated U.S.P.) this is:

U.S.P. Picks per Denier U.S.P. size diameter, inch of raw inches, max. silk used The picks per inch are the number of threads, running in one direction, per lineal inch of suture.

The silk is braided using a smaller number of picks than conventional, and with a larger core size. The braided'silk is washedto degurn, then dyed, if desired, in skeins in accordance with conventional practice. The silk is dried, and then dry stretched from. about 6% to about 11% of its length. This stretching tightens the braid, and gives a more dense, more handleable silk. At least some of the stretching may be accomplished while the silk is wet.

The raw silk used has a total of about 378 denier.

white felt.

After stretching the silk suture ,is passed through a solvent bath containing the polymeric silicone. Such solvents as xylene, toluene, benzene, gasoline, or other non-toxic volatile hydrocarbon solvents may be used. In addition to the silicone, beeswax, ethyl cellulose or a low molecular weight polyethylene may be dissolved and used as part of the coating. For the silicone rubbers, a catalyst is usually used to accelerate the curing rate. The standard organic peroxides, of which benzoyl peroxide is the most frequently used, are suitable catalysts, 2% to by weight of the polymer gives good results. The heat which sets the resin decomposes residual peroxides to give non-toxic products. For the hardened, flexible films, having a higher percentage of phenyl groups, heat alone can cure the silicone. Organo metallic driers such as zinc octoate, or iron stearate accelerates the cure. Nontoxic salts of metals with fatty acids are effective.

A 2% to 50% solids bath gives a satisfactory coating.

A 5% to solids concentration in the bath results in easier operating control. A 20% concentration is usually preferred. While an adequate pick up with a single coating bath is obtainable, more uniform distribution and coating can be obtained by using two or more baths, with heat curing between coatings. A cure temperature of at least 150 C. for 30 seconds gives a cure, al-

though longer times at lower temperatures, or a longer cure with less catalysts, etc. in accordance with standard practice in the silicone art may be used.

A total weight of coat of 2% to 20% by Weight of the fiber gives good characteristics. This percentage is called the pick up.

The sutures are shown in the attached drawings:

FIGURE 1 is a cross-section of a silicone coated suture.

FIGURE 2 shows a portion of an eight carrier on a 16 capacity carrier braider formed braid.

FIGURE 3 shows a portion of a sixteen carrier braid.

EXAMPLE 1 A silk suture is braided, using 8 carriers,'on a sixteen carrier braider, with 3 ends of 13 to 15 denier silk per carrier, and a core of 3 ends of 13 to 15 denier silk, and picks per inch, giving the skipped braid of FIGURE 2. (The denier is the weight in grams of 9000 meters of the strand.) The braided suture is washed to degum, then dried, while looped in skeins. The dry silk is stretched 9% of its length, which gives improved stifiness; and increases the density.

A silicone rubber sold as Silastic 9711 by Dow- Corning is milled into sheets of about /s-inch thick, and thereto while milling additionally is added 8.46% by weight of the rubberof a silicone fluid containing by weight benzoyl peroxide (Luperco ASF). After milling for an additional 5 minutes, the sheets are cut into small pieces and soaked overnight in xylene. The swollen silicone is stirred to a cream-like consistency, then diluted to 20% solids, and stirred until uniform.

The braided silk is immersed in a trough of the silicone solution at room temperature, then wiped over a piece of The coated silk is passed through a three stage heating tunnel, so that the silk is heated for one minute each at 100 C., 125 C., and 150 C. The silk is spooled after air cooling.

This coating procedure is repeated. In the double c'oa'ting, the'silk is found to have picked up 15% by weight of the silicone coating.

The finished suture gauges 0.0077 inch in diameter and is a 4-0 suture.

A conventional braiding of a 4-0 suture gives about 60 to 70 picks per inch, and uses 8 carriers with 2 ends of 20-22 denier each, and no core.- Such a silk suture has a total denier of about 336, and if coated with bees wax in accordance with conventional practice gauges .0083 inch.

length as to heat the silk suture for two minutes.

Other characteristics for comparison are:

Silk Silk With With New Old Silicone Beeswax Picks per i nch 40 60 Gauge:

Raw int-he 0076 0081 sterilized d0 0077 0083 Straight pull sterilized pounds 3. 17 2. 68 Knot pull sterilized do 2. 04 1.80 Pliaoility to bend, raw mgs 117 102 Stifinessinches self support Horizontal (sterile) inches 2. 94 4. 75 Vertical (sterile) do 4. 00 5.13 Apparent density as braided gms./cc- 1.127 0.927

The increase in strength after sterilization both straight and over a knot shows the new silicone construction to have marked advantages. 7

The suture is sterilized either by conventional autoclaving procedures, or by ethylene oxide gas, in accordance with commercial practice in the industry.

The individual silk filaments of the braid are shown at 10, the filaments of the core are shown at 11, and the suture has a silicone coating 12. FIGURE 2 shows the construction of a 000 suture, otherwise the same as above.

EXAMPLE 2 The coating of the suture of Example 1 is repeated using a 15% solids solution of a dimethy silicone polymer of the general formula (CH SiO) with 5% by weight of the polymer of benzoyl peroxide as catalyst. After two coatings, a readily handleable suture is obtained.

EXAMPLE 3 A multi-filament 4-0 sized silk suture braided as in Example 1 is washed and dyed black in accordance with conventional procedures. The suture is then dry stretched. An alkyl polysiloxane sold by General Electric as Drifilm 88 is diluted with toluene to form a 10% silicone solids solution. The silk suture is immersed in the toluene solution of the silicone resin at 50 C., then drawn through a curing tunnel at a temperature of C., and of such The suture may be heated longer, so as to sterilize thesuture at this time after which it is sterilely packed and handled until used by the surgeon; or after the two-minute heating, the suture may be reeled and packaged using clean but not sterile techniques and finally sterilized by dry heat after packaging and prior to sale, or just prior to use by the surgeon.

EXAMPLE 4 the coated silk is heated to 130 C. for three minutes. i

The silk suture may be sterilized by heating, as desired, but before use. About 12% by weight of the silk of the silicone remains in the coating.

EXAMPLE 5 The silicone rubber sold as Dow-Corning Silastic 9711 is milled with 4.2% of benzoyl peroxide for five minutes, out into small pieces, covered with xylene, and soaked overnight. The swollen material is stirred with additional xylene to obtain a 20% solids concentration.

Braided silk prepared as described in Example 1 is passed through the silicone in xylene, wiped with a piece of white felt, then cured for one minute each at temperatures of 100 C., 125 C., and 150 C. The silk picks up about A multi-filament size 3-0 braided polyester suturewas .coated in two passes with a silicone rubber bath containing 17% silicone solids dispersed in xylene. The coating and curing procedure was as described in Example 5. The suture picked up 2.9% by weight of silicone solids. The polyester suture iwas non-capillary.

EXAMPLE 7 A multi-filament 241 silk suture was braided using 16 carriers each containing 3 end denier silk; a core of 14 ends 20-22 denier silk; a pick count of and a total denier of 966. The construction is of the type shown in FIGURE 3. The braided suture was coated with a methyl phenyl polysiloxane which contains about 72% methyl groups and 28% phenyl groups. The coating bath con tained 35% silicone solids in xylol. The excess coating was wiped off with apiece of sponge rubber and the coating was cured for one minute each at temperatures of 100-C., 125 C., and 150 C. The silk picked up 7% by weight of silicone solids for one coat. A second coat under the same conditions yielded a total pick up of 12%. The silk at both coating levels Wasnon-capillary, had good bond and showed good resistance to brooming. Surgeons knots tied in the silk broke before slipping.

EXAMPLE 8 A multi-filament spun, or twisted, 3-0 silk suture was coated with a methyl-phenyl polysiloxane, processed and cured as in Example 7. The spun and twisted silk had a silicone pick up that ranged from 7% for a single coat to 12% for a double coat. The silk did not broom or bush and the filaments were bonded together, so that a needle could be readily threaded.

EXAMPLE 9 A multi-filament size 3-0 braided nylon suture was coated in two passes in a silicone rubber bath containing 17% silicone solids dispersed in xylene. and curing procedure was that described in Example 5. The nylon suture picked up 4.5% by weight of silicone solids and was non-capillary. Good results were obtained when used in surgery.

EXAMPLE 10 A multi-filament braided 3-0 suture was coated with a bath containing 30% solids of a silicone resin commercially sold as Dow-Corning 804. This resin is a comparatively short chain silicone resin containing both phenyl and methyl substitutents on the silicone atoms. Added to this bath was a plasticizer amounting to 20% of the weight of the silicone solids. The silk was immersed in this bath, the excess silicone wiped off with sponge rubber and the silicone was cured in a tunnel for one minute each at temperatures of 100 C., 125 C., and 150 C. The silk for a single coat had a silicone pick up of 7% of the weight of the silk. Silk with two coats had a pick up of 12% silicone resin- Silk coated in this resin bath and the added plasticizer had good hand, was'non-capillary and did not broom; Plasticizers' used' were alkyl aryl phosphates, phthalates, sebacates, citrates, epoxies and. polymeric dimethyl siloxanes;

The coating The polysiloxanes containing larger proportions of.

aryl groups require larger amountsof plasticizers. The

pick up can be readily varied by the pressure on the wipers. A slower. cure at a lower temperature gives a good coating. A more rapid cure is generally preferred, as the cure most conveniently takes place in a tunnel, and if a slower cure is used the tunnel must be longer for a given production rate and hence. is more expensive.

I claim:

1. A surgical suture comprising a plurality of individual silk filaments, the external silk filaments being in braided configuration, having a tight braid, with high density, having approximately the following construction: U.S.P. size 6-0; picks per inch 40; denier of raw silk used 112; and a coating on each silk filament of a non-toxic physiologically inert polymeric silicone, said silicone being present in an amount at least sufficient to impart noncapillarity and not more than 20% of the weight of the uncoated filaments.

2. A surgical suture comprising a plurality of individual silk filaments, the external silk filaments being in braided configuration, having a tight braid, with high density, having approximately the following construction: U.S.P. size 5-0; picks per inch 40; denier of raw silk used 252; and a coating on each silk filament of a non-toxic physiologically inert polymeric silicone, said silicone being present in an amount at least sufiicient to impart noncapillarity and not more than 20% of the weight of the uncoated filaments.

3. A surgical suture comprising a plurality of individual silk filaments, the external silk filaments being in braided configuration, having a tight braid, with high density, havingapproximately the following construction: U.S.P. size 4-0; picks per inch 40; denier of raw silk used 378; and a coating on each silk filament of a non-toxic physiologically inert polymeric silicone, said silicone being present in an amount at least sufiicient to impart noncapillary and not more than 20% of the weight of the uncoated filaments.

4. A surgical suture comprising a plurality of individual silk filaments, the external silk filaments being in braided configuration, having a tight braid, with high density, having approximately the following construction: U.S.P. size 3-0; picks per inch 40; denier. of. raw silk used 630; and a coating on each silk filament of a non-toxic physiologically inert polymeric silicone, said silicone being present in an amount at least sufiicient to impart noncapillarity and not more than 20% of the weight of the uncoated filaments.

5. A surgical suture comprising a plurality of individual silk filaments, the external silk filaments being in braided configuration, having a tight braid, with high density, having approximately the following construction: U.S.P. size 00; picks per inch 50; denier of raw silk used 966; and a coating on each silk filament of a non-toxic physiologically inert polymeric silicone, said silicone being present in an amount at least suificient to impart noncapillarity and not more than 20% of the weight of the uncoated filaments.

6. A surgical suture comprising a plurality of individual silk filaments, the external silk filaments being in braided configuration, having ;a tight braid, with high density, having approximately the following construction: U.S.P. size 0; picks per inch 50; denier of raw silk used 1560; and a coating on each silk filament of a non-toxic physiologically inert polymeric silicone, said silicone being present in an amount at least sufiicient to impart noncapillarity and not more than 20% of the Weight of the uncoated filaments.

7. The method of making surgical sutures comprising braiding a plurality of filaments of silk into a hard dense core, washing the gum from the braided silk, drying the braided silk, dry stretching the braided silk about 6. to 11% of its length, immersing the braided silk in a xylene solution of a polymerizable silicone, wiping the braided silk suture, whereby there is a silicone pick up of about to by weight, and drying and polymerizing said silicone.

8. The method of making surgical Sutures comprising braiding a plurality of filaments of silk into a hard dense core, washing the gum from the braided silk, drying the braided silk, dry stretching the braided silk about 6 to 11% of its length, immersing the braided silk in a solution of a polymerizable silicone rubber containing a catalyst, wiping the braided silk suture, whereby there is a silicone pick up of about 10% to 20% by weight, and drying and polymerizing said silicone by heat, of at least about 150 C. for at least about seconds, thereby also decomposing the catalyst.

9. The method of making surgical sutures comprising braiding a plurality of filaments of silk into a hard dense core, washing the gum from the braided silk, drying the braided silk, dry stretching the braided silk about 6 to 11% of its length, immersing the braided silk in nontoxic volatile hydrocarbon solvent solution of a polymerizable silicone rubber containing a catalyst, wiping the braided silk suture, drying and polymerizing said silicone, re-immersing in said solution, re-wiping the suture, whereby there is a total silicone pick up of about 10% to 20% by weight, and drying and polymerizing said silicone by heat, of at least about 150 C. for at least about 30 seconds, thereby also decomposing the catalyst.

10. A surgical suture comprising a plurality of individual silk filaments, the external silk filaments being in braided configuration, having a tight braid, with high density, having approximately the following construction: U.S.P. size 6-0; picks per inch denier of raw silk used 112; and a coating on each silk filament of a nontoxic physiologically inert polymeric silicone, said coating Weighing from 10% to 20% of the weight of the silk filaments.

11. A surgical suture comprising a plurality of individual silk filaments, the external silk filaments being in braided configuration, having a tight braid, with high density, having approximately the following construction: U.S.P. size 5-0; picks per inch 40; denier of raw silk used 252; and a coating on each silk filament of a nontoxic physiologically inert polymeric silicone, said coating weighing from 10% to 20% of the weight of the silk filaments.

12. A surgical suture comprising a plurality of individual silk filaments, the external silk filaments being in braided configuration, having a tight braid, with high density, having approximately the following construction: U.S.P. size 4-0; picks per inch 40; denier of raw silk used 378; and a coating on each silk filament of a nontoxic physiologically inert polymeric silicone, said coating weighing from 10% to 20% of the weight of the silk filaments.

13. A surgical suture comprising a plurality of individual silk filaments, the external silk filaments being in braided configuration, having a tight braid, with high density, having approximately the following construction: U.S.P. size 3-0; picks per inch 40; denier of raw silk used 630; and a coating on each silk filament of a nontoxic physiologically inert polymeric silicone, said coating weighing from 10% to 20% of the weight of the silk filaments.

14. A surgical suture comprising a plurality of individual silk filaments, the external silk filaments being in braided configuration, having a tight braid, with high density, having approximately the following construction: U.S.P. size 00; picks per inch denier of raw silk used 966; and a coating on each silk filament of a nontoxic physiologically inert polymeric silicone, said coating weighing from 10% to 20% of the weight of the silk filaments.

15. A surgical suture comprising a plurality of individual silk filaments, the external silk filaments being in braided configuration, having a tight braid, with high density, having approximately the following construction:

10 U.S.P. size 0; picks per inch 50; denier of raw silk used 1560; and a coating on each silk filament of a non-toxic physiologically inert polymeric silicone, said coating weighing from 10% to 20% of the weight of the silk filaments. V

16. A surgical suture comprising a plurality of individual filaments in coordinate configuration, the filaments being bonded together to hold the filaments in a unitary strand, and hence non-brooming, having a coating on each filament of a non-toxic, physiologically inert, polymeric silicone, whereby the suture is non-capillary and is inert towards livingtissue, the Weight of said silicone being from 10% to 20% of the weight of the uncoated filaments.

17. A surgical suture comprising a plurality of individual filaments selected from the group consisting of silk, nylon, polypropylene and stretched oriented polyester, the external filaments being in braided configuration, having a tight braid, and low pick count, with high density, thereby imparting surgically handleable char acteristics to the uncoated suture, and a coating on each filament of a non-toxic physiologically inert polymeric silicone, whereby the suture is non-capillary and is inert towards living tissue, the weight of said silicone being from 10% to 20% of the weight of the uncoated filaments.

18. A surgical suture comprising a plurality of individual silk filaments, the external silk filaments being in braided configuration, having a tight braid, and low pick count, with high density, thereby imparting surgically handleable characteristics to the uncoated suture, and a coating on each silk filament of a non-toxic physiologically inert polymeric silicone, whereby the suture is noncapillary and is inert towards living tissue, the weight of said silicone being from 10 %to 20% of the weight of the uncoated filaments.

19. A surgical suture comprising a plurality of individual silk filaments in coordinate configuration, each filament having thereon a coating of a polymethyl-polyphenyl siloxane, at least the final polymerization being in situ, the weight of said silicone being from 10% to 20% of the Weight of the uncoated filaments, whereby the suture is non-capillary and is inert towards living tissue, and the siloxane coating causes the filaments to adhere to each other, and thereby be free from brooming, and which suture, when tied in a surgeons knot, breaks rather than slips, on pulling in tension.

20. The method of making surgical sutures comprising braiding a plurality of filaments of silk into a hard dense core, washing the gum from the braided silik, drying the braided silk, dry stretching the braided silk about 6 to 11% of its length, immersing the braided silk in a xlyene solution of a polymeriza-ble silicone, wiping the braided silk suture, whereby there is a silicone pick up of an amount sufi'icient to render the finished suture non-capillary and not more than 20% of the weight of the uncoated -filaments,.and drying and polymerizing said silicone.

21. The method of making surgical sutures comprising braiding a plurality of filaments of silk into a hard dense core, washing the gum from the braided silk, drying the braided silk, dry stretching the braided silk about 6 to 11% of its length, immersing the braided silk in a solution of a polymerizable silicone rubber containing a catalyst, wiping the braided silk suture, whereby there is a silicone pick up of an amount sufiicient to render the finished suture non-capillary and not more than 20% of the weight of the uncoated filaments, and drying and polymerizing said silicone by heat, of at least about C. for at least about 30 seconds, thereby also decomposing the catalyst.

22. The method of making surgical sutures comprising braiding a plurality of filaments of silk into a hard dense core, washing the gum from the braided silk, drying the braided silk, dry stretching the braided silk about 6 to 11% of its length, immersing the braided silk in non-toxic sues #52 l. volatile hydrocarbon solvent solution ofa polymerizable silicone rubber containing a catalyst, Wiping the braided silk suture, drying and polymerizing said silicone, reimmersing in said solution, re-wiping the suture, whereby there is a total silicone pick up of an amount sufficient silicone, said silicone being present in an amount at least sufiicient to impart non-capillarity and not more than 20% of the Weight of the uncoated filaments, and the suture is inert towards living tissue.

24. A surgical suture comprising a plurality of individual filaments selected from the group consisting of silk,

nylon, polypropylene and stretched oriented polyester,

the external filaments being in braided configuration, having a tight braid, and low pick count, with high density, thereby imparting surgically handlea-ble characteristics to the uncoated suture, and a coating on each filament of a non-toxic physiologically inert polymeric silicone, said silicone being present in an amount at least sufiicient to impart non-capillarity and not more than 20% of the weight of the uncoat-e filaments, and the suture is inert towards living tissue.

25. A surgical suture comprising a plurality of individual silk filaments, the external silk filaments being in braided configuration, having a tight braid, and low pick count, with high density, thereby imparting surgically handleable characteristics to the uncoated suture,.and a coating on each silk filament of a non-toxic physiologically inert polymeric silicone, said silicone being present in.

an amount at least suificient to impart non-capillarity and not more than 20% of the weight of the uncoated filaments, and the suture is inert towards living tissue.

26. A surgical suture comprising a plurality of individual silk filaments in coordinate configuration, each filament havingthereon a coating of a polymethyl-polyphenyl siloxane, at least the final polymerization being in situ, the weight of said silicone being an amount sufficient to render the finished suture non-capillary and not more than 20% of the weight ofthe uncoated filaments, and said suture is inert towards living tissue, and the siloxane coating causes the filaments to adhere to each other, and thereby be free from brooming, and which suture when when tied in a surgeons knot, breaks rather than slips, on pulling in tention.

References Cited by the Examiner UNITED STATES PATENTS 2,193,188 3/40 Bradley 128-6355 2,588,365 3/52 Dennett.

2,698,817 1/55 G'uenther 28--80 2,734,506 2/56 Nichols et al. l28-335.5 2,737,075 3/ 56 Poirier et al 872 3,035,476 5/62 Fogden 87-9 V FOREIGN PATENTS 876,208 8/61 Great Britain. 1,110,824 7/61 Germany.

RlCHARD A. GAUDET, Primary Examiner. JORDAN FRANKLIN, Examiner.

Claims (1)

1. 23. A SURGICAL SUTURE COMPRISING A PLUTALITY OF INDIVIDUAL FILAMENTS IN COORDINATE CONFIGURATION, THE FILAMENTS BEING BONDED TOGETHER TO HOLD THE FILAMENTS IN A UNITARY STRAND, AND HENCE NON-BROOMING, HAVING A COATING ON EACH FILAMENT OF A NON-TOXIC, PHYSIOLOGICAL INERT, POLYMERIC SILICONE, SAID SILICONE BEING PRESENT IN AN AMOUNT AT LEAST SUFFICIENT TO IMPART NON-CAPILLARITY AND NOT MORE THAN 20% OF THE WEIGHT OF THE UNCOATED FILAMENTS, AND THE SUTURE IS INERT TOWARDS LIVING TISSUE.

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