IE922919A1 - Fluorescent synthetic sutures - Google Patents

Abstract

A synthetic, monofilament or multifilament surgical suture which is highly visible under normal and ultraviolet lighting conditions comprising a colored flurorescent dye incorporated therein. The dye imparts a distinctive color to the synthetic suture under visible light and will fluoresce with a bright color upon exposure to ultraviolet light. The dyed synthetic suture, particurlarly a nonabsorbable suture of multifilament construction, is especially adapted for external wound repair to greatly enhance identification and ensure complete suture removal.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the utilization of a fluorescent material in surqical sutures. More Darticular1v. the Dresent invention pertains to hiqhlv visible, synthetic sutures for external wound repair which fluoresce with a distinctive visible color upon exposure to an ultraviolet liqht source. 2. Description of the Prior Art Suture materials for external surqical procedures are qenerallv fabricated from nonabsorbable filaments extruded from such synthetic polymers as polyesters, polyolefins or polyamides, for example. Due to its hiqh flexibility and tensile strenqth, multifilament nylon particularly finds wide acceptance as a typical nonabsorbable suture material, especially in the field of veterinary medicine. However, multifilament nylon surqical sutures for external wound stitchinq are usually available only in either clear or white opaaue which renders them visually undetectable when utilized on liqht skinned or coated animals. especially those with white or tan fur. This problem concermnq visibility is compounded when animals presented for suture removal exhibit an early regrowth of the light, hairy coat surroundinq the wound which has been stitched. Furthermore. the white nylon sutures are often soiled bv the animal after application, causinq the sutures to turn a dirty brown or darker color which may be practically indistinguishable from the im ini 'P tt * ',n rt tz « ss? 7 oriqinailv colored coat. This lack of contrasting colors noses serious DroPlems with reqard to identification which are not encountered in other surqical applications. such as internal wound reoair using absorbable suture materials. For instance. failure to completely remove all fragments of the nonabsorbable suture material after the wound has sufficiently healed mav Dromote tissue irritation which can directly result in stitch abscess or other adverse bodily reactions over an extended period of time.

In order to enhance the visibility of surgical liqatures, it has been Droposed to provide sterile filaments having a succession of lines or dots of contrasting shades on its surface. as disclosed in U.S. Patent No. 3,949,755 to Vauouois (issued April 13. 1976). The disclosed liqatures mav be easily placed in position bv the surgeon since the shaded filaments can be readily seen throuqh a film of blood. While such surqical ligatures are generally effective during internal suturing Drocedures such as tying small vessels, the aforementioned problems associated with suture identification and removal in external applications remains largely unaddressed.

SUMMARY OF THE INVENTION It is, accordingly, a primary object of the present invention to provide surqical sutures for external wound reoair which are highly visible under normal and ultraviolet lightinq conditions to qreatly enhance identification and ensure complete suture removal .

It is a further object of the invention to provide a method of suturing which utilizes colored suture filaments that will fluoresce with a bright color upon exposure to ultraviolet light 291 9 in oraer to markedly ennance suture visibility.

It is amonq the additional ob.iects of the Dresent invention to Drovide a method of Dreoarinq monofilament or multifilament sutures having the desired degree of visibility and flexibility derived from fluorescent dved synthetic Dolymers. The Dresent dyed sutures not only retain their mechanical Drooerties for a time sufficient for the wound to heal, but also significantly lessen tissue irritation by increasing suture recognition without leaving harmful residues in the sewn tissue.

These and other ob.iects are accomDlished in accordance with the Dresent invention which orovides a surgical suture comorising a sterile, synthetic filament containing a colored fluorescent dve. wherein said synthetic filament exhibits a distinctive color under visible light and fluoresces with a bright color of fluorescence during exDOSure to ultraviolet radiation. The visibly colored sutures of the Dresent invention. Darticularlv synthetic nonabsorbable, multifilament sutures, are esDecially adaDted for external wound reDair. For this DurDose. it is Dreferred to use fluorescent dyes with a wide range of desirable shades such as bright yellow, orange, green or fuchsia when viewed under normal and ultraviolet lighting conditions.

In a soecific embodiment, the colored fluorescent dyes employed in the invention are incorporated throughout the filament suture material by immersion in a dye bath to Drovide a brightly colored suture permeated with a fluorescent pigment which is not removed by abrasion. The colored fluorescent sutures are readily visible for positive identification to enhance suture adjustment or removal and thereby substantially avoid tissue inflammation and other adverse reactions. 29 1 9, The foregoing and other features, advantages and otner objects of the invention may De more fully aoDreciated dv reference to the followinq detailed descriDtion. should adverse DETAILED DESCRIPTION OF THE INVENTION As synthetic oolvmers suitable for the present suture filament. various materials have been considered, the essential requirements being that thev Dossess adequate tensile strength, be capable of sterilization, and exhibit the necessary degree of flexibility, surface smoothness and knot security. The synthetic suture material should also be dimensionally uniform over a Deriod of time sufficient for the wound to heal and storagestable in the dry state. In addition, these suture materials not leave any undesirable residues which may Dromote tissue reactions. As such. monofilament and multifilament, synthetic nonabsorbable suture materials of polyethylene tereDhthalate, do!ydtody1ene and nylon, for examole, are Dreferablv used. Because of its ready availability, cost and long-standing use bv veterinary Dractitioners for external the preferred suture material is Nylon is a Dolvamide of orotein-like structure prepared from an aliphatic dicarboxvlic acid, such as adipic acid or sebacic acid, and aliphatic diamines such as hexamethvlene diamine which can be extruded into filaments. The resulting nylon sutures are usually of braided. twisted or multifilament construction.

In an alternative embodiment, filaments extruded from absorbable suture materials which deqrade enzymatically can also be used in the present invention if they fulfill the above requirements. The absorbable suture materials should not surgical procedures. nonabsorbable nylon. »2291Ϊ1 disappear from the sewn tissue Defore the wound nas completely healed, which mav be as long as a vear in certain externa' aDD1ications. for examole. Those absorbable materials that disappear within a substantially shorter Deriod or orior to wound healing were found to be undesirable since such sutures incorporated with the oresent dves may leave a dve residue in the sewn tissue after the suture itself is absorbed. Therefore. extruded collaqenous materials such as ordinary catgut are not Darticularlv favorable for the Durposes of the invention since they lose their mechanical properties ouite rapidly and induce unwanted tissue reactions unless they can be modified to retard their absorption rate, as will be discussed in more detail hereinafter.

Synthetic absorbable suture materials which are subject to biodegradation such as polylactide, polyglvcolide. copolymers of lactide and glycolide. poly(p-dioxanone), and mixtures of such polymers may be suitable in the oresent invention if they meet the above orereouisite characteristics, especially regarding absorption rate. The incorporation of fluorescent dyes into these particular absorbable materials alters their chemical properties such that the biodegradation of the dyed suture product may be significantly retarded for a period sufficient to enable the sutured wound to heal. The present synthetic absorbable sutures may also be coated with conventional suture coating materials such as silicon or beeswax in order to further modify the handling and adsorption rate of the dyed sutures.

In an additional embodiment of the invention, the absorbable suture filament may be coated with a Drotective sneath consisting of a mixture of the dve material ana a resin that is hydrolytically degradable but is enzvmatical 1v stable. Suitable resins for this SDecific embodiment are disclosed in U.S. Patent No. 4.433.688 to Bichon. In Dractice. the dve-resin coating can be modified to have a thickness which varies debending on the particular application. Thus, when an external wound is stitched with the instant coated or sheathed suture filament. the dveresin coating can be made to partially degrade hydrolytically very slowly such that the suture core remains dimensionally stable until the wound heals. Then, when the coating of dve and resin has been partially degraded but clearly visible. the absorbable core is attacked by the body enzymes and is absorbed.

As is common with biological systems, the rate of absorption varies from patient to patient and with the thickness or molecular weight of the absorbable core. Thus, a wide range of absorption rates and molecular weights are possible to meet different applications. Care should be taken to ensure that no significant amounts of undesirable residues be left in the tissue.

For practical purposes, any fluorescent dve material which imparts color under visible light to the suture filament and which emits highly visible color in certain wavelength ranges when excited by ultraviolet radiation (UV) may be suitable in the present invention. The color of fluorescence emitted by these dve materials in the solid state may be substantially similar to or completely different from the color exhibited under visible light. As examples of such suitable dye materials. particular reference is made to the daylight fluorescent dyestuffs of the rhodamine. sulforhodamine, naohthalimide or xanthene series.

These specific dyestuffs or pigments are well known and are im & described in the Encyclopedia of Chemical Technology. Second Edition. Vol. 9. (1966). John wilev and Sons. Inc. Daylight fluorescent pigments are more highly visible than non-davliqht fluorescent dyestuffs because the emitted light combines additively with the reflected color to provide sutures having the best possible brilliancy under either visible or UV light. Thus, with the use of these preferred dyes, other nonf1uorescent colorants may not be needed to achieve the desired color under either visible or ultraviolet light conditions. However, it is possible to use a mixture of one or more fluorescent dyes with a nonf1uorescent pigment to produce the desired color effect in the visible range. For some purposes, it may be desirable to use fluorescent materials which are colorless when viewed under visible light and emit fluorescent light in a certain range under UV.

The daylight fluorescent dyes used in the present invention are commercially available in a variety of bright colors such as red. blue, yellow, orange, green, purple and Dink, for example. from such sources as the Hercules Powder Co., Glen Falls, NY: Lawter Chemicals, Inc., Chicago, IL: Radiant Color Co., Richmond.

CA: and Day-Glo Color Corp., Cleveland, OH.

The sutures of the present invention may be formed by incorporating the fluorescent pigments in the polymeric suture material prior to extrusion or during preparation of the suture product. Thus, an effective amount of a colored fluorescent dyestuff is added to a liauid suture monomer mixture, wnich is then polymerized to produce individually dyed filaments for the manufacture of the present monofilament or mu 1tifi1 ament sutures.

The fluorescent dyes are distributed throughout the mass of the polymer structure and will not leach from the suture material »229 during storage or use. The dyestuff concentration generally ranges between aoout 0.1 and 10 percent bv weight, depending on the degree of brilliancy desired.

In a preferred method, the present sutures can be prepared bv immersing extruded monofilament or multifilament synthetic sutures in a dye bath to form a color-permeated suture product in which the fluorescent material is not subject to settling out or being worn off during use. The basic method involves the immersion of the extruded sutures in a bath comprising an aqueous solution of ammonium and sodium sulfate, a surfactant, and an effective amount of the fluorescent dye. The surfactant added to the bath may be any suitable liauid detergent, but it is preferred to use diethvlene glycol since this specific surfaceactive agent results in dyed sutures of greater tinctorial strength. The bath is then heated to boiling with occasional stirring and acidified by adding glacial acetic acid. The sutures are then removed from the bath, washed, and dried to provide a product in which the fluorescent dye is actually diffused throughout the formed filaments and is not merely on surface thereof.

The amount of fluorescent dye incorporated into the suture material may vary by controlling certain parameters of the method of dyeing, e.g.. the concentration of the dye in the bath during boiling, the duration of the dyeing reaction, the suture materials employed, and the like. In general, the concentration of dye in the bath will range from as little as about 1 percent by weight to as much as about 15 percent or higher in some cases. The amount of dye actually distributed throughout the suture filament to produce a fluorescent effect may vary considerably — 92 2 919 and generally ranges from as low as about 0.000001% ud to as much as about 10% by weight of the dved suture. In most instances. the dve will penetrate sufficiently into the suture structure to give a deep color which is not prone to deterioration. Of course, in dyeing multifilament sutures, it is not necessary that every filament within the suture be individually or completely impregnated with the dye material.

Sterilization of the dyed sutures may be subseauently accomDlished by exposure to heat or sterilizing agents such as gamma rays, ethylene oxide gas. cobalt 60, and the like without any significant loss of properties. It is also possible to sterilize the suture material at any time prior to. during or after formation of the final suture structure.

As indicated hereinabove, the surgical sutures of the present invention find wide applications, especially amongst veterinary practitioners for external wound stitching. However, due to their increased visibility and fluorescent Drooerties, the present sutures may find general acceptance amongst dentists, oral surgeons and ophthalmologists for suture identification purposes. As an indirect advantage, pediatric surgeons will no doubt find that the disposition of their voung patients will significantly improve from use of the brightly colored sutures of the invention, especially if the children are given the opportunity to select their favorite color. Also, plastic surgeons will appreciate the benefits of the present highly visible sutures and the accompanying assurance of knowing that complete suture removal can be attained by a auick check with any convenient fluorescence-sensing device.

The fluorescent sutures of the present invention will 9229 1 9 produce visible light of a particular wavelength upon being excited bv means of a light source which produces ultraviolet energy within an appropriate spectral band. For practical purposes, any UV light source device such as a small mercury vapor lamp may be utilized in connection with the present i nvention.

The following Examples further illustrate the invention, wherein parts and percentages are bv weight unless specifically stated otherwise.

EXAMPLE 1 There were mixed together in a 500 ml. Erlenmever flask, 200 ml. of water, 400 mg. of ammonium sulfate, 200 mg. of sodium sulfate and 0.2 ml. of diethylene glycol to form an aaueous solution. To this solution was added 300 mg. of a fluorescent dyestuff of the rhodamine series, available from Day-Glo Color Coro, under the name Grand Yellow 0-834. Several strands of multifi1 ament nylon sutures measuring about 6 cm in length each are placed in the dye solution and the resulting mixture is brought to boil by heating the flask over an open burner. The mixture is then boiled gently for 20 minutes with occasional agitation. At this time. 0.2 ml. of glacial acetic acid is added to the mixture, which is boiled for an additional 30 minutes.

The suture strands are then removed from the mixture, rinsed in water and allowed to dry.

The above sutures appeared bright yellow when viewed in daylight and exhibited a brilliant yellow color when observed under ultraviolet light.

EXAMPLE 2 922 9 1 gThe procedure of Example 1 was repeated, except that the fluorescent dyestuff emoloved was Erio-acid red (acid red-52) available from Burlington Chemical. The dyed nylon sutures of this example showed a pink-tinted color which fluoresces 'hot oink under ultraviolet light.

Using 150 mg. of the dye of Example 1 in combination with 50 mg. of the above dve, sutures were prepared having a visible orange color. When viewed in ultraviolet light, the sutures fluoresced a brilliant yellowish orange color.

EXAMPLE 3 To a 500 ml. Erlenmeyer flask containing 200 ml. of water. 400 mg. of ammonium sulfate, 200 mg. of sodium sulfate, 0.2 ml. of diethylene glycol and two threads of multifi1 ament nylon sutures, each measuring 8 cm in length, is added 180 mg. of the nonf1uorescent pigment Acid Blue #9 available from Pylam Products Co. The resulting mixture is boiled for 10 minutes and 200 mg. of the fluorescent dyestuff Grand Yellow D-834 is then added, whereupon boiling is continued for about 15 minutes with stirring. Glacial acetic acid (0.2 ml.) is added and the mixture is boiled for an additional 30 minutes. The suture threads are then removed from the mixture, rinsed in water and allowed to dry.

The above sutures show a dark green color which under ultraviolet light had a bright yellowish green appearance.

The visible color of the present sutures may be modified dy the addition of other nonfluorescent pigments in combination with other fluorescent dves. Other suitable fluorescent dyes include FDA certified dves such as Drug and Cosmetic Red #28 (color index name Acid Red 92) and Yellow #8 (color index name Acid Yellow 9229 ) .

It will be apparent that sutures produced in accordance with the foregoing method may be sterilized and finally packed, either dry or in alcohol-containing wrappers, for subsequent use in various external surgical procedures. Thus, it has been found that the brightly colored sutures of the oresent invention are highly visible for positive identification. The surgical practitioner may then know immediately upon visual inspection whether all fragments of the suture material have been completely removed and take the necessary action.

The present invention also provides a suture filament which is simple and inexpensive to manufacture. When evaluated under actual use conditions, the present surgical sutures exhibited excellent dye retention and tensile properties. They were further demonstrated to posses an appropriate slick surface to enable auick and easy suture work and, simultaneously, prevent knot slippage.

It should be understood that there may be made various changes and modifications of the representative embodiments herein chosen for purposes of illustration without departing from the spirit and scope of the invention. Accordingly, the forgoing illustrations are not to be interpreted as restrictive of the invention beyond that necessitated by the following claims. 9229ι 9

Claims (9)

CLAIMS I claim:

1. A surgical suture of improved visibility comprising a sterile, synthetic filament having incorporated therein an effective amount of a colored fluorescent dve. said synthetic filament exhibiting a distinctive color under visible light and adapted to fluoresce with a bright color of fluorescence during exposure to ultraviolet radiation.

2. The surgical suture according to Claim 1 wherein the synthetic filament is a nonabsorbable polvmer of multifi1 ament I construction.

3. The surgical suture according to Claim 2 wherein said nonabsorbable polymer is nylon.

4. The surgical suture according to Claim 1 wherein the color exhibited under visible light and the color of fluorescence are substantially similar.

5. The surgical suture according to Claim 4 wherein the color of fluorescence is selected from the group consisting of red, blue, yellow, orange, green, purple and pink.

6. The surgical suture according to Claim 1 wherein the colored fluorescent dye is a daylight fluorescent dyestuff of the rhodamine, sulforhodamine. naphthalimide or xanthene series.

7. The surgical suture according to Claim 1 wherein the colored fluorescent dve is diffused throughout the synthetic filament bv immersing extruded monofilament or mu 1tifi1 ament synthetic sutures in a dye bath to form a col or-permeated suture 92 2 9 lisj oroduct.

8. 8. The surqical suture according to Claim 1 wnerein the synthetic filament additionally contains a nonf1uorescent pigment to modify the color exhibited under visible light.

9. A surgical suture according to any preceding claim substantially as hereinbefore described.