WO1996034565A1 - Non absorbable type suture for internal use - Google Patents

Abstract

A non absorbable type surgical suture for internal use comprises a braid, characterised in that the braid (6, 8) is made of non lubricated strands of which about 85 to 50 % by weight are conventional surgical sutures, and of which about 15 to 50 % are strong strands made from a biomaterial with a knotting resistance lower than that of said conventional sutures, such that the suture provides the required knot strength through at the most four half-hitches.

Description

 Non-absorbable suture thread with internal use

The invention relates to the field of sutures used in surgery and in particular, a suture thread for internal use and of the non-absorbable type. This wire is in particular intended for heart valves or vascular prostheses.

It is known that there are two kinds of suture threads: absorbable threads and non-absorbable threads which remain in the body or which are removed, these two kinds of threads being used in substantially identical proportions.

In the group of nonabsorbable yarns, more than half are monofilaments. The rest is made up of braids in silk, polyamide or polyester-based threads. It can be noted that some of these threads, in particular those of silk or polyamide, decompose after a few years, and are therefore not suitable for certain applications.

The non-absorbable braided threads are often rough, which leads to many drawbacks. First of all, they have a saw effect when the surgeon uses them. In particular, they can create, in fragile fabrics, holes wider than the diameter of the wire. In addition, to perform the suture, the surgery forms knots. It can be seen that with rough threads, the positioning of the nodes is not easy.

Consequently, these braids often undergo a treatment to lubricate the wire and thus improve its fastening characteristic, that is to say the ease and regularity with which one can slide a knot on the suture in place.

Mention may in particular be made of treatments based on silicone resin, Teflon, fatty acid esters, polybutylates or also beeswax.

The various pharmacopoeias require the purity of the sutures but are not concerned with lubricants. However, the quantity of lubricant present on the wire is generally around 5% and it is found that as soon as the knot is made and after the wire has been introduced into the body, particles of the lubricant can come off the wire. A good part of these lubricant products comes off and moves through muscle movements. The particles coming from the nonabsorbable sutures are themselves nonabsorbable and are then encysted, infiltrated with cellular reaction or possibly cause interactions with elements of blood.

These particles are not harmless and many surgeons are aware of the problems that can arise from the products they introduce into the human body through sutures.

These problems are posed in an increased manner for vascular prostheses where very great cleanliness is required, in particular to avoid rejection reactions. The present invention therefore aims to provide a new surgical suture thread for internal use and non-absorbable which slides sufficiently without damaging the tissues and allows the sliding and the easy formation of the nodes, while ensuring the maintenance of the nodes, once formed, and avoiding any introduction into the human body of unwanted particles.

According to the invention, the suture comprises a braid made up of non-lubricated strands, of which approximately 85 to 50% by weight are conventional surgical sutures and of which approximately 15 to 50% by weight are resistant strands, produced in a biomaterial and whose knotting resistance is lower than that of said conventional threads and such that said suture thread holds the knot in at most four half-keys.

The knot resistance parameter is assessed by means of the test which will be described below. It consists of measuring the force that the surgeon should exert to bring the wire down.

The second parameter is the number of half-keys required to block a node. This parameter can be determined by another test described below.

It can be seen that the suture thread according to the invention, obtained from a mixture of non-lubricated threads, has the properties generally required of a surgeon for a suture thread and above all, for a thread used in cardiovascular surgery. and which are as follows:

- good sliding of the wire through the fabrics, without sawing or braking effect,

- an easy descent of the nodes without snagging, - a possibility of correcting the position of the half-made node, in order to give it its final location with the tension on the edges of the wound it wishes, a blocking of the node obtained by 1, 2, or several additional half-keys. This blockage must be permanent and resist muscular efforts, shearing and even alternative movements of the heartbeat. In general, the surgeon performs at most four half-keys, sometimes with an additional half-key, for safety.

The suture thread according to the invention has the properties generally required for this type of thread, while avoiding the use of additional lubricating products. Any risk of introducing unwanted particles into the human body is therefore eliminated.

The knotting resistance parameter for a given thread is determined by the test described in document EP-0 279 666, the content of which is included in the present application.

This test, known as the Yoshito test, consists in interlacing two sutures of the type to be tested, a first free end of each of the two wires being linked to a fixed point. The second free end of a wire is passed around a roller and attached to a weight, used to create traction and whose value is generally between approximately 50 and 100 g. The second free end of the other wire passes around another roller and a force (F) is applied to this end.

The value of the force (F) necessary to slide the knot formed between the two sutures is recorded continuously. The average value obtained corresponds to the resistance to knotting. Thus, the lower the value of the force (F), the more the resistance to knotting is low and the more the fixing is carried out gently.

It should be noted that the Yoshito test is a method of assessing resistance to knotting.

The values obtained depend on parameters other than the intrinsic slip of the wire tested and in particular

- the size of the wire (diameter), - the number of stitches per centimeter,

- the number of strands used for braiding,

- strand tension and

- the title of the fibers used.

The parameter of the number of half-keys necessary to ensure the blocking of a node is determined by the following test. It consists in carrying out, with the thread to be tested, a loop of thread 1 with a knot 2, consisting of several inverted half-keys 3, for example four, as illustrated in FIG. 1. The knot 2 is then tightened to 70 % of the strength of the wire. The tight knot is illustrated in Figure 2.

A force is then applied tending to open the loop from the inside, for example by maintaining the fixed loop at 4 and by applying a force at 5, by means of a dynamometer, not shown in FIG. 2.

If it is found that the node 2 rolls and opens, then the number of half-keys is insufficient to ensure the blocking of the node. On the other hand, if the knot tightens, blocks and holds, the number of half-keys is sufficient to ensure the blocking of the knot. Experience has shown that this test can indeed be applied to surgical practice.

Preferably, the braid comprises 15 to 50% by weight of threads having a knotting resistance of between 0.150 and 0.250 daN, according to the Yoshito test (weight 0.100 daN).

Preferably, the braid making up the suture is regular. Thus, the characteristics on the sliding state of the suture are as uniform as possible.

It is also possible to make the braid so that the threads having the lowest knotting resistance are located mainly on the surface of the braid.

This increases the slip of the suture.

It is also advantageous if the suture has a core. This makes it possible to obtain a round braid. It also provides solidity and held over the suture.

The wire constituting the core can be of the same nature as the wires forming the braid. It can also be made of another material usually used as a ligature or suture.

The core thread increases the resistance of the braid. It can comprise one or more fibers, in the latter case, the fibers are preferably cabled.

Furthermore, the number of threads constituting the braid is chosen according to the diameter which it is desired to obtain for the suture thread.

A braid is conventionally made up of 4, 6, 8, 10, 12 or 16 strands. By way of example of resistant threads, produced from a biomaterial and having an appropriate knotting resistance, mention may be made of threads based on high performance polyethylene (PEHP). This material, already used as a biomaterial to make ligaments, is inert and not biodegradable.

In these yarns based on high performance polyethylene which have been recently developed, it has been possible to increase the crystallinity and the molecular weight of the polyethylene and to better orient its macromolecular structure. By a gel-based extrusion process, fibers that can be braided are obtained and very strong strings can be obtained. The strength of these threads is more important than that of the most efficient materials, such as aramids.

The PEHP yarns have a knotting resistance of the order of 0.170 daN and are therefore very suitable for making the yarn according to the invention. By way of example of conventional non-lubricated surgical suture threads, mention may be made of polyester or polyamide threads, without particles or lubricant.

Polyester (PET) based on polyethyl glycol and therephthalic acid has been known for years and used in the form of a braid in surgery. Its long-term resistance is appreciable. However, the wires have a saw effect when the surgeon uses them, and the positioning of the knots is not easy. This is also why the polyester threads used in surgery are lubricated, to increase their sliding coefficient or even decrease their resistance to knotting. According to other preferred modes of the invention:

the braid comprises a third component in the form of strands mixed with the braid and / or in the form of a core inside the braid, said strands being in the form of fibers or of monofilament.

- one of the components of the braid or of the core is capable of reducing capillarity and / or provides bactericidal or bacteriostatic properties.

For example, the presence of a cellulosic thread, such as a flax thread, in the core makes it possible to reduce the cappilarity throughout the braid.

The invention will be better understood and other objects, advantages and characteristics thereof will appear more clearly on reading the following description of nonlimiting examples of embodiment of the invention, made in particular with regard to Figures 3 and 4 which represent sutures according to the invention. Example 1

Referring to Figure 3, the yarn 6 consists of a mixture of polyester yarns and high performance polyethylene yarns. The suture was dyed after it was made. Only the polyester threads take the dye, which allows them to be identified.

The wire consists of:

- 4 PEHP wires of 110 dtex and

- 8 polyester threads of 113 dtex. The weight ratio, in the braid, of the threads used is therefore:

- 32.74% of PEHP yarn and

- 67.26% polyester yarn. On the other hand, the suture in Figure 3 has a core thread 7 of 235 dtex which has been made visible on the upper part of Figure 3. The diameter of the wire is 0.46 mm. The test described in document EP-0 279 666 leads to a value of the knotting resistance of 0.225 daN, for a weight of 0.100 daN.

The value of the second parameter (number of half-keys) is 4, at 14.79 daN. Example 2

The suture has a shape similar to that shown in Figure 3.

It is made up of :

- 4 PEHP threads of 55 dtex and - 8 polyester threads of 74 dtex.

The weight ratio, in the braid, of the threads used is therefore:

- 27.10% of PEHP yarn and

- 72.90% polyester yarn. The suture thread includes a core thread, made up of two cabled PEHP threads of 55 dtex.

The knotting resistance of this second example of wire is 0.233 daN, according to the test of document EP-

0 279 666, for a weight of 0.100 daN. The value of the second parameter is 4 half-keys at 9.22 daN.

Example 3

The suture consists of: - 3 PEHP threads of 55 dtex and

- 9 polyester threads _. of 74 dtex.

The weight ratio, in the braid, of the threads used is therefore: - 19.36% of PEHP yarn and

- 80.14% polyester yarn.

The suture thread includes a core thread made up of two cabled PEHP threads of 55 dtex. The knotting resistance is 0.243 daN, for a weight of 0.100 daN according to the test of document EP-0 279 666.

The value of the second parameter is 4 half-keys at 9.21 daN. It can be seen that with these three wires, the knot is positioned correctly: with two half-keys, the surgeon can correct his knot, after four half-keys in total, the knot remains blocked. We can also refer to Figure 4 which illustrates a wire according to the invention consisting of a flat braid 8, without core wire.

The numerous tests carried out show that in the ranges 15-50% by weight for non-lubricated threads having an appropriate knotting resistance such as PEHP threads and 85-50% by weight for conventional non-lubricated threads, of the polyester type, can obtain a suture thread allowing both a good descent of the knots and a correct blocking of the knot made.

All the values indicated above are grouped in the attached table. For comparison, the corresponding values are included for two yarns (Reference yarn 1 and reference yarn 2) made up of a braid of 10 polyester yarns of 74 dtex with a PET core yarn, 113 dtex, and for a polyester thread coated at 1% by weight (thread reference 3) and at 5% by weight (thread reference 4). It is found, for example, that the knotting resistance of a suture thread according to the invention is lower than that of a conventional polyester thread coated with PTFE. In addition, the reference thread 4 which is a conventional polyester thread coated with PTFE, requires four half-keys to ensure the blocking of the knot, like the threads of Examples 1, 2 and 3, which are threads in accordance with the invention. The present invention therefore avoids the use of additional lubricant products. By mixing two different types of thread, the hybrid suture thread according to the invention provides at least the same sliding and blocking qualities of the knot after it has been made by the surgeon as conventional lubricated threads. This result is obtained thanks to the intrinsic qualities of the two wires used.

The reference signs inserted after the technical characteristics mentioned in the claims, have the sole purpose of facilitating the understanding of the latter, and in no way limit their scope.

BOARD

REF. PET PEHP Resistance to Dia. Half-keys required for

% by weight% by weight knot for one (10 ~ -) blocking of the knot weight of 0.100 daN 3 4 5 6 (daN)

Example 1 67.26% 32.74% 0.225 46.00 14.79 daN Example 2 72.90% 27.10% 0.233 32.42 9.22 daN Example 3 80.14% 19.36% 0.243 32.47 9.21 daN

Reference wire 1 100% 0.305 31.88 3.58 daN

Reference wire 2 100% 0.350 39.70 7.21 daN (number of different meshes)

Reference wire 3 100% 0.261 32.52 7.85 daN PTFE coated (1%)

Reference wire 4 100% 0.261 32.62 7.18 daN PTFE coated (4%)

Claims

1. Surgical suture of the non-absorbable type and for internal use composed of a braid, characterized in that said braid (6, 8) consists of non-lubricated strands, of which approximately 85 to 50% by weight are conventional wires of surgical sutures and of which about 15 to 50% by weight are resistant strands, made of a biomaterial and having a knotting resistance lower than that of said conventional threads and such that the suture thread ensures the holding of the knot by at most four half - keys. 2. Suture according to claim 1, characterized in that the braid comprises approximately 15 to 50% by weight of threads having a knotting resistance of between 0.150 and 0.250 daN, according to the Yoshito test (weight 0.100 daN). 3. Suture according to one of claims 1 or 2, characterized in that the braid is regular. 4. Suture thread according to one of claims 1 to 3 characterized in that the threads having the lowest knotting resistance are mainly found on the surface of the braid. 5. Suture according to one of claims 1 to 4, characterized in that it comprises a core, in particular consisting of one or more threads of the same kind as those constituting the braid. 6. Suture according to one of claims 1 to 5, characterized in that the braid comprises 15 to 50% by weight of high performance polyethylene, in the form of strands. 7. Suture according to one of claims 1 to 6, characterized in that the braid comprises 85 to 50% by weight of polyester or polyamide son, without particles or lubricant. 8. Suture according to one of claims 1 to 7, characterized in that the braid comprises a third component in the form of strands mixed with the braid and / or in the form of a core inside the braid, said strands in the form of fibers or monofilament. 9. Suture according to one of claims 1 to 8, characterized in that one of the components of the braid or of the core is of a nature to reduce capillarity and / or provides bactericidal or bacteriostatic properties.