US 2751910 A
Description (OCR text may contain errors)
United States Patent SUTURES Edward L. Howes, New York, N. Y.
No Drawing. Application June 25, 1953,
Serial No. 364,205
6 Claims. (Cl. 128-3355) This application relates to sutures to be used in surgery which can be boiled or sterilized by heat in the usual autoclave and yet are self-sterilizing to the degree that they will resist bacterial contamination when placed in the wound and will tend to destroy bacteria in their location in the tissues, thereby reducing the possibility of infection in the wound. My sutures have high tensile strength, good workability and are more readily encapsulated in the tissues than the sutures usually employed. They also show very little danger of secondary extrusion.
The sutures of this invention comprise a fibrous base preferably of twisted silk or cotton impregnated with a dilute solution of an organic filler material such as a proper plastic or high melting point wax which when dried and hardened will withstand boiling, together with a very small percentage of anti-bacterial agent which preferably has some tendency to combine with the proteid of the silk.
Thus far I have found only one type of plastic which is soluble in a volatile solvent which is available for my purpose, and which will withstand the sterilizing treatment. This is a combination of vinylidine chloride and vinyl chloride sold under the trade name of Saran B. The use of a soluble impregnating material is important because by forming a dilute solution the plastic material can be carried into the very fibers of the support medium and distributed through the support medium without filling the interstices between the separate strands which would tend to give the support medium a somewhat slick surface. It is important that the suture retain the normal appearance and structure of the fibrous thread so that granulations may grow into it whereby the suture will become fixed in the tissue. While I prefer to use a soluble plastic, as stated, I can also obtain valuable results by using soluble waxes having a melting point substantially above 100 C. Most of these waxes are synthetic and are sold under trade names such as Acrowax C, Alcowax and Stantowax P. A natural wax that can be employed is cranberry wax.
Bactericidal substances which may be employed include the phenyl mercuric salts such as phenyl mercuric chloride, phenyl mercuric benzoate, phenyl mercuric acetate and phenyl mercuric borate. Other bactericidal agents which may be used and which fall in the group defined above include the salts of sulfamylon such as the hydrochloride and the mandelate salts.
The solvent selected should be volatile and preferably should be a solvent for both the plastic or waxy material and the anti-bacterial agent. My preferred solvents are tetrahydrofuran or 1-4 dioxane. Other solvents that may be employed include cyclohexanone and cyclopentanone but if these are used with waxes they should be employed hot, as waxes tend to settle out at room temperature.
In forming the suture, a dilute solution of the Saran in the solvent is prepared which may contain, for example, between 2% and 5% by weight of solids. With this is included from about .01% to .025 (preferably about .02%) of the bactericidal agent. The fibrous support, which as stated is preferably twisted thread of silk or cotton of a type appropriate for use in sutures, is then drawn through the solution. Excess liquid is allowed to drain off and the solvent is then dried out. With tetrahydrofuran the evaporation takes place almost immediately, whereas with dioxane it may be desirable to dry the suture with some slight heating before it is wound on a reel, say at a temperature of about C.
I have found that a suture such as described has great benefits. First, on the purely mechanical side, the impregnation permits me to use a twisted thread rather than a braided one without danger of-the ends fraying. A twisted thread in and of itself is stronger than a braided thread and the impregnation appears to add to the strength so that the impregnated twisted thread of my invention is approximately 20% stronger than a coresponding unimpregnated braided thread. The impregnation also gives some stiffness to the suture making it easier to use in the operating room. The use of a twisted thread rather than a braided one is also valuable because with the twisted thread encapsulation has been found to take place about fifteen days earlier than with the braided thread. In ordinary case twisted threads fray out too readily to be generally useful but this is largely prevented by the impregnatron.
While the mechanical improvements of my suture are valuable, the most important feature is found in the antibacterial qualities. The plastic or waxy material tends to hold the bactericidal agent in place so that it is not readily removed during sterilization and this is further assisted by the aifinity between the bactericidal agent and the proteid in the silk. At the same time the solid impregnating material is sufficently porous (perhaps due to the fact that a low concentration solution was employed and the solvent subsequently evaporated off) so a sufficient amount of the bactericidal agent gradually finds its way to the surrounding tissues, with the result that bacteria in the neighborhood of the suture are destroyed and the possibility of infection in the wound is much reduced. I have found, for example, that the mercuric salts are particularly useful as they are destructive against both gram positive and gram negative bacteria. At the same time their solubility is relatively low and they do not provoke unnecessary tissue reactions and are not toxic, allergenic or carcinogenic. Encapsulation takes place rapidly and the threads become firmly fixed in the tissues. There is no more inflammatory reaction than with the unimpregnated sterilized thread and there is a marked reduction in the bacteria surrounding the thread so that post-operative extrusion or sloughing is greatly minimized.
In making my suture I prefer to use the binder and bactericidal materials in one single bath as has been described but valuable results can be obtained if two separate baths are used, in which case each solvent may be employed for the two impregnating materials. In such case the thread is preferably impregnated with the dilute solution of bactericidal agent and then with the binder material. It is understood that in any case the amount of impregnating material employed will be insufiicient to coat the thread as a whole by entirely filling the depressions between the strands, or to substantially increase its diameter.
What I claim is:
1. A surgical suture consisting of a thread of natural fiber which retains the appearance and structure of the thread but which is impregnated with a small percentage of an anti-bacterial agent and a material of a plastic nature that is soluble in an organic solvent so that it may be applied in a dissolved state and which is substantially unaffected by being boiled in water, such material being selected from the group consisting of the plastic formed by the combination of vinylidine chloride and vinyl chloride, and the high melting point waxes and such material being used in an amount insufiicient to fill the interstices betweenthe strands of the thread to render the surface of the thread slick and impermeable.
2. A suture as specified in claim 1 in which the antibacterial agent is a phenyl mercuric salt.
3. A suture as specified in claim 1 in which the thread is twisted silk.
4. A surgical suture consisting of a twisted thread of silk impregnated but not coated with a small percentage of phenyl mercuric salt and the plastic formed by the combination of vinylidine chloride and vinyl chloride.
5. The method of preparing a suture which comprises forming a dilute solution in an organic solvent of an antibacterial agent and a material of a plastic nature which is substantially unafiected by being boiled in water, such material being selected from the group consisting of the plastic formed by the combination of vinylidine chloride and vinyl chloride and the high melting point waxes, impregnating a thread of natural fiber With such solution in an amount such that the solution is insufiicient to fill the interstices between the fibers and thereby render the surface of the thread slick and impermeable to water and drying.
6. A method as specified in claim 5 in which the antibacterial agent is a phenyl mercuric salt and the plastic material employed is the plastic formed by the combination of vinylidine chloride and vinyl chloride and in which the solution contains between about 2% and 5% of solids including between about .01% and .025 of the phenyl mercuric salt.
References Cited in the file of this patent UNITED STATES PATENTS 1,202,931 Watson Oct. 31, 1916 1,741,893 Watson Dec. 31, 1929 1,942,061 Hofmann Jan. 2, 1934 2,099,688 Hill Nov. 23, 1937 2,567,905 Field Sept. 11, 1951