RU2275210C2 - Surgical suture thread and method for manufacturing it - Google Patents

Abstract

FIELD: medical engineering.

SUBSTANCE: thread has warp as monofilament or polyfilament thread and bioinert polymer coating. Every filament has coating in the amount of 0.25-5% of warp mass. Poly-para-xylylene is selected as coating material. Monofilament or polyfilament warp is treated in gas under pressure below the atmospheric one. Treatment is carried out in para-xylylene medium at 10-100 Pa and temperature of 10-30°C.

EFFECT: improved bioinert properties; high strength; improved manipulation properties.

2 cl, 13 dwg

Description

The invention relates to surgical suture materials, namely multifilament non-absorbable sutures for joining soft biological tissues by suturing.

Monofilament yarns in the form of a single fiber with a thickness of several hundred micrometers and multifilament yarns of many fine fibers with a thickness of several micrometers each are known. Natural and synthetic materials are used as the basis of threads.

Monofilament yarns are characterized by high strength and bio-neutrality, which contributes to the absence of capillary and wick effects. The disadvantage of such filaments is increased stiffness, which leads to injury to biological tissues and worsens the handling properties, such as knotting.

On the contrary, multifilament yarns obtained by twisting or weaving thin fibers have good handling properties, but in comparison with monofilament yarns, their bio-neutrality is low, and it is difficult to thread the tip of the thread into the needle.

Silk / Buyanov V.M., Egiev V.N., Udotov O.A. Surgical stitch. Moscow, Rapid-Print, 1993, 100 pp., Pp. 4-9 /, viscose / Yurkshtovich N.K., Chekhovskiy A.K., Golub N.V., Kaputsky F.N. The influence of oxidation conditions in the system of nitric oxide (IV) - carbon tetrachloride on the mechanical properties of viscose yarns // Journal of Applied Chemistry, 2001, v. 74, issue 10, S.1696-1700 /, hard shell of the spinal cord of animals / Pat. Russia №2033187, 6 A 61 L 17/00. Surgical thread and method for its production, publ. 1995; Pat. Russia No. 2033810, A 61 L 17/00. A method of obtaining a surgical suture thread, publ. 1995 /, catgut / Shadrin V.V., Teplikov A.V. Handling characteristics of surgical threads // Russian Journal of Biomechanics, 2001, v.5, No. 3, S.41-50 /. The advantages of natural-based threads are close values of the pulling force of the needle and thread, low traumatism, a minimum number of knots for reliable fixation when tying, and high elasticity. However, they are characterized by instability of mechanical characteristics, biodegradation, and the possibility of infection of the connected tissues.

Threads based on synthetic (usually polymeric) materials, in particular polyesters / Pat. Russia No. 2066200, A 61 L 17/00. Surgical suture thread, method for its manufacture and device for implementing the method, publ. 1996 /, polyamide / A.S. USSR No. 1609212, D 01 F 11/04, A 61 L 17/00. A method of obtaining antimicrobial filaments, publ. 1994 /, polypropylene / A.S. USSR No. 1241554, A 61 L 17/00. Surgical suture material based on a polymer and method for its preparation, publ. 1995 /, have significant mechanical strength and biostability, but are characterized by significantly different efforts to pull the needle and thread. However, monofilament synthetic yarns have low handling characteristics, and multifilament yarns have a sawing effect on the connected biological tissues. Reflow of a portion of a thermoplastic synthetic yarn to facilitate needle filling according to US Pat. US No. 4832025, A 61 L 017/00. Thermoplastic surgical suture thread with a fused section, publ. 1989 does not eliminate the noted deficiencies.

These shortcomings are partially overcome in natural and synthetic suture materials with a composite structure, consisting of a base (core) and a modifying coating, which use carboxymethyl cellulose / Pat. Russia No. 2065752, A 61 L 17/00. A method of obtaining a resorbable surgical thread, publ. 1996 /, chitosan / A.S. USSR No. 94030883/14, A 61 L 17/00. Suture material, publ. 1997 /, a combination of layers of polyvinyl alcohol and chitosan / A.S. USSR No. 93054862/14, A 61 L 17/00. Suture material, publ. 1996 /, a copolymer of N-vinylpyrrolidone / Pat. Russia No. 2065753, A 61 L 17/00. A method of manufacturing surgical suture materials, publ. 1996 /, polyurethane / Titova G.E. Thes. doc. 3 scientific symp "Synthetic polymer materials for medical purposes", Belgorod-Dniester, 1977, p.12. /, caprolactam copolymers / А.с. USSR No. 1609212, D 01 F 11/04, A 61 L 17/00. A method of obtaining antimicrobial filaments, publ. 1994; Pat. USA No. 6616687, MKI A 61 B 017/04. Surgical suture thread, publ. 2003 /, polyester / Pat. US No. 4510934, MKI A 61 L 017/00. Suture thread, publ. 1985 /, fluororubber / Pat. Russia No. 1587726, A 61 L 17/00. Suture surgical thread, publ. 1990 - prototype / etc.

The lack of coverage using chitosan / A.S. USSR No. 94030883/14, A 61 L 17/00. Suture material, publ. 1997; A.S. USSR No. 93054862/14 A 61 L 17/00. Suture material, publ. 1996 / is its destruction in the body, which makes it difficult to obtain non-absorbable suture material; N-vinylpyrrolidone copolymer coating / Pat. Russia No. 2065753, A 61 L 17/00. A method of manufacturing surgical suture materials, publ. 1996 / has low adhesion and strength, and the coating is made of polyurethane / Titova G.E. Thes. doc. 3 scientific symp "Synthetic polymer materials for medical purposes", Belgorod-Dniester, 1977, p.12 / is not sufficiently inert to biological environments.

In the patent / A.S. USSR No. 1609212, D 01 F 11/04, A 61 L 17/00. A method of obtaining antimicrobial filaments, publ. 1994 / describes a multifilament yarn of polycaproamide coated with a copolymer of caprolactam, hexamethylene diammonium adipionate and hexamethylene diammonium sulfoisophthalate with the addition of an antibiotic. However, the polymers used to form the coating have polar chemical groups, as a result of which the thread shows a strong capillary effect. Possible infection of the wound is suppressed by an antibiotic, which can cause an allergic reaction. Since the caprolactam copolymer is the base component of the coating, only polyamide yarns can be used as the base. Similar disadvantages have a surgical suture thread coated with a homopolymer or a copolymer of caprolactam with calcium stearate / Pat. USA No. 6616687, MKI A 61 B 017/04. Surgical suture thread, publ. 2003 /.

In the patent / Pat. US No. 4510934, MKI A 61 L 017/00. Suture thread, publ. 1985 / a composite filament with a monofilament core and an outer layer in the form of a braid from a biocompatible polymer is proposed. The ability to remove the core after the formation of the seam facilitates knitting, however, this design of the thread significantly complicates the technology for its preparation and increases the cost.

The closest in technical essence to the proposed solution is a surgical thread / Pat. Russia No. 1587726, A 61 L 17/00. Suture surgical thread, publ. 1990 - a prototype. /, Consisting of a core of polyester and a shell of fluororubber, carbon black, magnesium oxide, benzoyl peroxide and pigment with a mass ratio of core: shell of 1: 0.5 ... 4. The coating has increased adhesion to the base, strength and resistance to bending. Fluororubber has the highest bioinertness among rubbers.

However, the prototype has the following disadvantages:

- the use of a large amount of impregnating material in accordance with the proposed mass ratio "core: sheath" leads to a significant increase in the thickness of the thread and the deterioration of handling properties;

- a reactive agent (benzoyl peroxide) may not be fully used in the crosslinking reaction, which reduces the bioinertness of the shell.

To obtain composite yarns, various methods for the formation of modifying coatings have been proposed.

In the known method / Pat. Russia No. 1776100, D 01 F 6/46, D 01 F 11/04, D 06 M 16/00, D 06 M 101: 20, A 61 L 17/00. A method of obtaining biologically active surgical filaments, publ. 1995 / proposes to form a coating of chitosan from a solution of the latter in acetic acid, which narrows the field of application of polyester filaments and a limited number of acid-resistant polymers, eliminating the possibility of modifying silk, polyamide and other materials that are not resistant to acids. In addition, the method does not allow penetration of the modifier into the multifilament base and coating of individual fibers. This leads to monolithization of the warp, which significantly increases the stiffness of the thread during bending and complicates knitting. A similar disadvantage is the method / Titova G.E. Thes. doc. 3 scientific symp "Synthetic polymer materials for medical purposes", Belgorod-Dniester, 1977, p.12. /, according to which polyester (dacron) yarns are modified by impregnating the warp with polyurethane rubber.

There are methods aimed at modifying individual fibers of a multifilament yarn. These include oxidative modification of viscose yarn with nitrogen oxides / Yurkshtovich N.K., Chekhovsky A.K., Golub N.V., Kaputsky F.N. The influence of oxidation conditions in the system of nitric oxide (IV) - carbon tetrachloride on the mechanical properties of viscose yarns // Journal of Applied Chemistry, 2001, v. 74, issue 10, S.1696-1700. /. The use of gas-phase processing significantly increases the uniformity of the modification of fibers both on the surface and in the depth of the thread. However, during oxidation, the strength of the thread is reduced by 1.5-3 times, causing the need to increase its thickness, which leads to injury of the seam. The method is applicable only to cellulose fibers - viscose, cotton, etc.

In a known technical solution / Pat. Russia No. 2065753, A 61 L 17/00. A method of manufacturing surgical suture materials, publ. 1996 / the original thread is immersed in a hot (40 ... 100 ° C) solution of the polymer composition with an exposure of 1-15 hours and subsequent drying. The disadvantage of this method is the multi-stage and the likelihood of bonding fibers.

Similarly, get the thread of the patent / A.S. USSR No. 1609212, D 01 F 11/04, A 61 L 17/00. A method of obtaining antimicrobial filaments, publ. 1994 /, in which a multifilament yarn from polycaproamide is passed through a weak (0.1-0.7%) alcohol solution of a copolymer of caprolactam, hexamethylene diammonium adipionate and hexamethylene diammonium sulfoisophthalate containing antibiotics. The excess solution is removed by extraction, and then dried in two stages at a temperature of about 70 and 140 ° C. The method is optimized only for coating polyamide yarns and does not exclude the bonding of fibers with each other with the formation of quasimonofilament yarns.

In the patent / Pat. Russia No. 1776100, D 01 F 6/46, D 01 F 11/04, D 06 M 16/00, D 06 M 101: 20, A 61 L 17/00. A method of obtaining biologically active surgical filaments, publ. 1995 / thread, obtained from a melt of a mixture of polypropylene and polystyrene, is sulfonated with a solution of chlorosulfonic acid in carbon tetrachloride. Then antibiotics and other biologically active substances are grafted onto the thread. However, the strength decreases and the handling properties of the thread are deteriorated due to the inevitable embrittlement of the polymer. The method is applicable only to the mixture of fiber-forming polymers indicated in the patent.

Closest to the technical nature of the proposed technical solution is a method of modifying surgical suture threads / Pat. Russia No. 1709620, A 61 L 17/00. Suture surgical thread, publ. 1994 - the prototype. /, According to which the processing is carried out by a nonequilibrium low-temperature plasma in argon at a pressure below atmospheric. In the prototype, a fairly uniform treatment of all fibers of the thread is achieved without gluing the latter. Threads of any material may be processed. Under the influence of plasma, the surface of the thread is additionally cleaned, which contributes to its sterility.

The disadvantage of the prototype is the lack of improved frictional properties of the filament and a decrease in the strength of the polymeric material of the filament under the action of plasma. Plasma activation of the surface, improving wetting, leads to an increase in the capillary effect and a decrease in bio-neutrality.

The objectives of the invention are:

- a decrease in the capillary effect and an increase in the bio-neutrality of multifilament yarns on a different (natural and synthetic) basis;

- increase the mechanical strength of the threads in the biological environment;

- reduction and alignment of the values of the coefficients of rest friction and movement when the thread slides along the biological tissue;

- improving the handling properties of threads;

- elimination of the destruction and bonding of the fibers of the base material during the modification process.

The solution of these problems is achieved by the fact that according to the claimed technical solution, the surgical suture thread consists of a warp in the form of a monofilament or multifilament thread and a coating of bio-neutral polymer, and the coating has each fiber, and the coating material is poly-para-xylene in the amount of 0.25- 5% by weight of the base.

The solution of these problems is also achieved by processing a monofilament or multifilament base in a gas medium at a pressure below atmospheric, and processing is carried out in a para-xylylene medium at a pressure of 10-100 Pa and a temperature of 10-30 ° C.

The poly-para-xylylene (PPC) polymer material used as a modifier, approved for endoprosthetics, has a high bio-neutrality. Polymerization is carried out from the gaseous medium, bypassing the liquid phase, which eliminates coating defects caused by uneven wetting of the edges and the formation of menisci. As a result, a conformal (equal-thickness) coating is formed even on a highly developed surface, including capillaries, protrusions and fibers with a characteristic size of several micrometers. Fixation of poly-para-xylylene is achieved mainly due to the enveloping (encapsulation) of individual fibers and to a lesser extent due to adhesion. The relatively weak adhesion of the PPC and the use of a small amount of this modifying polymer prevents the bonding of the fibers and helps to reduce the friction of the modified threads on the biological tissue. Thus, optimal localization of the functional coating in the form of a thin barrier layer on each fiber is achieved, which provides a solution to the problems of the invention.

Figure 1 shows a diagram of an installation for coating; figure 2 shows a diagram of a tensile test of threads; figure 3 shows a diagram of the deformation of a thread based on silk before and after modification in the presence (dashed lines) and absence (solid lines) of nodes; figure 4 shows a diagram of the deformation of the yarn-based filament before and after modification in the presence (dashed lines) and absence (solid lines) of nodes; figure 5 shows the effect of coating thickness on the tensile strength of silk threads in a dry and wet state; 6 shows the effect of coating thickness on the tensile strength of capron filaments in the dry and wet state; 7 shows a diagram of the testing of threads for friction; on Fig shows a typical kinetics of the friction force when stragging and subsequent pulling; Fig. 9 shows the effect of coating thickness on the pulling force of lavsan filaments in dry and wet conditions; figure 10 shows the effect of the thickness of the coating on the average pulling force of yarns from dacron in dry and wet condition; figure 11 shows the dependence of capillarity on the number of AUC applied to the base of capron; on Fig shows a micrograph of nylon filament without coating; on Fig shows a micrograph of kapron filament coated with a PPK coating in an amount of 6 wt.%.

In accordance with the claimed technical solution, twisted threads were modified on the basis of silk, polyamide (kapron) of two grades and polyethylene terephthalate (lavsan) with different coating thicknesses corresponding to the contents of 1 and 4 wt.% PPK.

When applying a poly-p-xylylene coating, an apparatus assembled on the basis of the VUP-4 universal vacuum post was used (Fig. 1). The installation includes a preliminary vacuum pump 1; high vacuum pump 2; valve system 3; nitrogen trap 4; a vacuum chamber 5 connected to an ionization-thermocouple vacuum gauge 6 type VIT-2; film thickness control system 7; reactor 8; a sublimator 9, a power source for the reactor 10 and a power source for the sublimator 11.

The coating is as follows. Modifiable suture material in the form of segments of threads 12 is placed in chamber 5. Using a preliminary vacuum pump 1 and a high-vacuum pump 2, air is pumped out to a vacuum of 10 ^-2 Pa, recorded by a vacuum gauge 6. Switching is carried out using a valve system 3. Protection of the gas medium in the chamber from oil vapor is produced using a nitrogen trap 4. In the reactor 8 and chamber 5, the pressure of the active monomer (para-xylylene) is created. The reactor 8 is powered by a source 10. The sublimator was heated electrically from a power source 11.

Registration of the coating thickness is carried out using the measuring system 7. After the coating is formed, the chamber 5 is evacuated and the modified threads are removed.

Surgical threads before and after modification were tested in vivo for biocompatibility. Comparative tests on experimental animals allowed us to establish a decrease in inflammatory reactions in the suture zone due to the hydrophobic effect of very small amounts of PPC, which virtually eliminated capillary transport of biological fluids along the thread. Studies in biological media infected with microorganisms showed a significant decrease in the wick effect. This is especially noticeable with the modification of twisted silk threads, which, due to insufficient bio-neutrality, go out of use in practical surgery.

Static tensile strength of threads, incl. with knots, and the pulling force of the threads in the dry and wet state before and after the modification was determined on the ComTen 94C and INSTRON 5567 test benches.

In the tensile test, the yarn samples were fixed, as shown in FIG. 2, in the upper and lower grips of the bench using elastic gaskets to prevent slipping and breakage of the thread near the edges of the grippers. To assess the impact on the strength of the nodes, the latter were performed in an amount of ten with an interval of 1 cm. The initial distance between the grips was 6 cm and the loading speed was 1 cm / min.

Typical strand deformation diagrams of twisted yarns are shown in FIG. 3, and yarn strength comparison results are shown in FIGS. 4 and 5. In particular, it can be noted that the nodes contribute to fiber consolidation, linearization of the diagram and prevention of breakage of individual fibers until the yarn is exhausted. If the presence of nodes significantly increases the strength of the silk thread (figure 4), the strength of the synthetic thread based on lavsan is somewhat reduced (figure 5).

A comparison of the ultimate tensile loads before and after applying a coating of PPK of various thicknesses is made in FIG. 6, where the strength of a dry thread without coating is taken as 100%. It is seen that the modification leads to a noticeable increase in the strength of the threads in the dry state and, more importantly for non-absorbable surgical threads, its preservation in wet conditions. This effect is more noticeable for twisted silk threads, in which the loss of strength during wetting is about 25%. This is explained by the encapsulating effect of the coating, which prevents softening of silk fibers under the influence of moisture, and also reduces the role of defects and the probability of damage to peripheral fibers. Improvement of the handling properties of the thread is also confirmed on the basis of the experience of performing sutures with modified threads on experimental animals.

When carrying out frictional tests, the force required to draw the suture along the suede surface of the sample of dressed skin was recorded as an imitator of living biological tissue (Fig. 7). The tests were carried out as follows: between the grips in a horizontal position, a cylindrical mandrel with a diameter of 40 mm was attached, wrapped with a leather flap 18 cm long. After fixing the end of the thread in the movable grip of the testing machine, one revolution was made around the mandrel, and a weight of 50 g was suspended to the second end of the thread. The loading rate was 10 mm / min.

As shown in Figs. 8 and 9, the application of a very thin coating of PPK (mass fraction of 1%) leads to a decrease in the friction force of the threads (for lavsan by 1.5 times) in the dry and wet state both when straining and when pulling. The stability of the frictional characteristic indicates that the strength of the coating is sufficient to maintain its continuity during short-term sliding on biological tissue under the conditions of formation of a surgical suture.

The effect of stragging is also reduced (manifested in the fact that the friction of rest exceeds the friction of sliding of the thread on the biological tissue), which improves the handling properties when performing the seam (Fig. 8). Knitting of knots is facilitated since low yield strength of the PPK contributes to the fixation of the node when it is tightened.

The increase in the mass of the coating PPC to 4% has a more noticeable effect on the force of breaking in the dry state and to a lesser extent on the force of breaking in a humid environment (Fig.9). The different nature of the change in the pulling force with increasing coating thickness (Fig. 10) is apparently due to the preservation of the minimum amount of PPC as a solid lubricant during the kinetic friction of dry threads and its gradual removal during friction in a humid environment.

Friction reduction is also observed subjectively when suturing and knotting knots. As a result, the degree of trauma of the suture material, especially silk, is reduced. In this case, the valuable handling properties of the silk base are used, which is securely fixed by only two nodes and is characterized by stable strength.

During the formation of the PPC coating, the hydrophobicity of the thread sharply decreases. 11 shows the dependence of capillarity, determined according to GOST 3816-81 “Textile fabrics, methods for determining hygroscopic and water-repellent properties”, on the amount of PPC applied to the base in the form of surgical thread No. 3 made of polyamide (kapron). Similar results were obtained for other types of framework. It can be seen that when the PPC content exceeds 0.25 wt.%, The thread capillarity decreases sharply, and at 1 wt.% PPC the thread becomes hydrophobic. On this basis, the lower limit of the content of the PPC, equal to 0.25 wt.%.

The upper limit of the mass content of PPC in the inventive surgical thread, equal to 5%, is determined by two factors. The first is that with such a content of PPC, a continuous coating is formed that consolidates the warp fibers and turns the original multifilament yarn (Fig. 12) into a quasimonofilament yarn (Fig. 13), which is a drawback. The second factor is determined by the criterion “efficiency-cost” and consists in a sharp increase in the cost of the obtained thread, since the cost of the PPK is 100-200 times higher than the cost of the base.

When forming the PPC coating according to the claimed method, the main technological parameters are the temperature and pressure of the monomer (para-xylylene).

When the temperature of the substrate (base) above 30 ° C, the polymerization of para-xylylene stops. At low (less than 10 ° C) temperature, the polymerization rate sharply increases and the uniform thickness of the coating decreases. In addition, cooling in a vacuum a thin thread with a low heat capacity is difficult and leads to a rise in the cost of the process.

An increase in pressure above 100 Pa leads to a loss of equal thickness of the coating on the fibers due to the high polymerization rate. At low (less than 10 Pa) pressures, the rate of coating formation is very low, which leads to a decrease in the efficiency of the process.

Thus, the application of the proposed technical solution provides high bio-neutrality, increased strength and improved handling properties of surgical sutures based on natural and synthetic materials.

Claims (2)

1. A suture surgical suture consisting of a warp in the form of a suture and a polymer coating, characterized in that a monofilament or multifilament suture is used as the suture, each fiber of the suture has a coating, and polyparaxylene in the amount of 0.25- is used as a polymer coating. 5% by weight of the base. 2. A method of obtaining a suture surgical suture, comprising treating the base in a gas medium at a pressure below atmospheric, characterized in that a monofilament or multifilament base is taken as the base, para-xylylene is used as the gas and the treatment is carried out at a pressure of 10-100 Pa and a temperature 10-30 ° C.

Images