Method for forming a barbed suture and the barbed suture thus obtained

Abstract

The invention relates to a method for forming a barbed suture (10) comprising: a) producing a knit by knitting together i) a set of chain stitch yarns (1) producing chain stitches and ii) a set of monofilament weft yarns completing weft stitches with at least one of said chain stitches, thereby producing at least one weft stitched chain stitch (6), b) cutting the knit along the warp direction on both sides of said weft stitched chain stitch, so as to isolate said weft stitched chain stitch from the rest of the produced knit, the chain stitch yarn of said at least one weft stitched chain stitch forming the elongate body (9) of the barbed suture and the monofilament cuts (7) extending from said weft stitches of said one weft stitched chain stitch forming the barbs (8) of said barbed suture.

Claims

1. A method for forming a barbed suture comprising an elongate body provided with barbs extending substantially radially out from said elongate body, said method comprising the following steps: a) producing a knit on a warp knitting machine comprising at least two guide bars, a first guide bar B1 and a second guide bar B2, by knitting together i) a set of chain stitch yarns of a first biocompatible material threaded in said first guide bar B1 and producing chain stitches and ii) a set of monofilament weft yarns of a second biocompatible material threaded in said second guide bar B2, the a knitting pattern followed by the second guide bar B2 producing at least a partial weft in which said monofilament weft yarns complete weft stitches with at least one of said chain stitches, thereby producing at least one weft stitched chain stitch, b) cutting the knit along the warp direction on both sides of said at least one weft stitched chain stitch, so as to isolate said weft stitched chain stitch from the rest of the knit, the chain stitch yarn of said at least one weft stitched chain stitch forming said elongate body of said barbed suture and the monofilament weft yarns cuts being cut and extending from said weft stitches of said at least one weft stitched chain stitch forming said barbs of said barbed suture.

2. The method of claim 1, wherein the knitting pattern followed by the second guide bar B2 produces at least a partial weft in which said monofilament weft yarns complete weft stitches with a plurality of chain stitches, thereby producing a plurality of weft stitched chain stitches, and wherein the cutting of step b) is repeated for each weft stitched chain stitch, thereby producing a plurality of barbed sutures.

3. The method of claim 1, wherein during step a), said second guide bar B2 is fed intermittently with said set of monofilament weft yarns.

4. The method of claim 1, wherein said first guide bar B1 is threaded 1 full, 1 empty along a whole width of the machine.

5. The method of claim 1 wherein the knitting pattern followed by the second guide bar B2 produces a partial weft in which said monofilament weft yarns complete from about 4 to about 15 weft stitches/cm along a length of each said weft stitched chain stitch.

6. The method of claim 1, further comprising a stretching step during which either the knit produced in step a) or the isolated weft stitched chain stitch (resulting from step b) is submitted to a stretching treatment.

7. The method of claim 1 wherein the isolated weft stitched chain stitch is submitted to a twisting treatment.

8. The method of claim 1, further comprising a heat-setting step during which either the knit produced in step a) or the isolated weft stitched chain stitch resulting from step b) is submitted to a heat-setting treatment.

9. The method of claim 1, wherein the first biocompatible material and the second biocompatible material are each selected from the group consisting in polyethylene, polypropylene, polyester such as polyethylene terephthalates, polyamide, silicone, polyether ether ketone (PEEK), polyarylether ether ketone (PAEK) polylactic acid (PLA), polycaprolactone (PCL), polydioxanone (PDO), trimethylene carbonate (TMC), polyvinyl alcohol (PVA), polyhydroxyalkanoate (PHA), polyglycolic acid (PGA), copolymers of these materials, and mixtures thereof.

10. The method of claim 1, wherein the second biocompatible material is polypropylene.

11. The method of claim 1, wherein the chain stitch yarns are multifilament yarns.

12. The method of claim 1, wherein the chain stitch yarns are polyethylene multifilament yarns having a tensile strength ranging from about 25 cN/dTex to about 40 cN/dTex.

13. The method of claim 1, wherein the monofilament weft yarns show a diameter ranging from 0.07 mm to 0.3 mm.

14. The method of claim 1 wherein a knitting pattern followed by bars B1 and B2 is the following according to the ISO 11676 standard: Bar B1: 0.1/0.1/1.0/1.0// Bar B2: 0.0/4.5/9.9/5.4// wherein B1 is threaded 1 full, 3 empty, and B2 is threaded 1 full, 7 empty, along the whole width of the machine.

15. The method of claim 1, wherein the a knitting pattern followed by bars B1 and B2 is the following according to the ISO 11676 standard: Bar B1: 0.1/1.0// Bar B2: 9.9/5.4/0.0/0.0/4.5/9.9// wherein B1 is threaded 1 full, 3 empty, and B2 is threaded 1 full, 7 empty, along the whole width of the machine.

16. The method of claim 1, wherein the chain stitch yarns are polyethylene multifilament yarns having a tensile strength of about 35 cN/dTex.

17. A method for forming a barbed suture comprising an elongate body provided with barbs extending substantially radially out from said elongate body, said method comprising: a) knitting together a set of chain stitch yarns of a first biocompatible material and a set of monofilament weft yarns of a second biocompatible material to form a knit, wherein the monofilament weft yarns complete weft stitches with at least one of the set of chain stitch yarns thereby producing at least one weft stitched chain stitch, b) cutting the knit along a warp direction on both sides of said at least one weft stitched chain stitch, so as to form cut monofilament weft yarns on both sides of said at least one weft stitched chain stitch, the chain stitch yarn of said at least one weft stitched chain stitch forming said elongate body of said barbed suture and the cut monofilament weft yarns extending from said weft stitches of said at least one weft stitched chain stitch forming said barbs of said barbed suture.

18. The method of claim 17 further comprising stretching, twisting, or both of the at least one weft stitched chain stitch to position the cut monofilament weft yarns in a desired configuration.

19. The method of claim 18 further comprising heat-setting the at least one weft stitched chain stitch to fix the barbed suture in a set configuration.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The advantages of the method of the invention will appear more clearly from the following examples and attached drawings in which:

(2) FIG. 1 is a schematic view showing a first embodiment of a knitting pattern suitable for the knitting process of step a) of the method of the invention,

(3) FIG. 2 is a schematic view showing a second embodiment of a knitting pattern suitable for the knitting process of step a) of the method of the invention,

(4) FIG. 3 is a schematic view showing the cutting step of the method of the invention,

(5) FIG. 4 is a front view showing a barbed suture obtained by the method of the invention,

(6) FIG. 5 is a partial front view of a barbed suture obtained by the method of the invention showing the angle formed between the monofilament cuts and the yarn forming the elongate body,

(7) FIG. 6 is a partial schematic view of a barbed suture obtained by the method of the invention having active and passive portions along its length.

DETAILED DESCRIPTION OF THE EMBODIMENTS

EXAMPLES

Example 1

(8) A knit is produced on a raschel machine wherein the knitting pattern followed by bars B1 and B2 is the following according to the ISO 11676 standard: Bar B1: 0.1/0.1/1.0/1.0// Bar B2: 0.0/4.5/9.9/5.4//

(9) wherein B1 is threaded 1 full, 3 empty, and B2 is threaded 1 full, 7 empty.

(10) The yarns threaded in guide bar Bar 1 are multifilament yarns of ultra high molecular weight polyethylene, such as those marketed by the company DSM under the tradename Dyneema Purity. These multifilaments have a tensile strength of 35 cN/dTex.

(11) The monofilaments threaded in guide bar Bar 2 are polypropylene monofilaments having a diameter of 0.25 mm.

(12) With reference to FIG. 1 showing the knitting pattern above in accordance with a representation well known for one skilled in the art, are shown the warp direction Wa, the weft direction We, the chain stitch yarns 1 (threaded in guide bar B1) and the monofilament weft yarns 2 (threaded in guide bar B2). The knitting pattern produces a plurality of chain stitches 3 and a partial weft 4. The weft yarns 2 complete weft stitches 5 with some of the chain stitches 3, herein after called weft stitched chain stitches 6. Actually, as appears from FIG. 1, the knitting pattern produces one weft stitched chain stitch 6 out of two chain stitches 3 present in the knit. In the present example, the distance between two adjacent weft stitched chain stitches 6 is due to the threading-in of the first guide bar B1, which is 1 full, 3 empty. Such a threading-in may result in a distance between the weft stitched chain stitches 6 of about 0.5 cm.

(13) With reference to FIG. 3, is shown schematically a piece of knit 12 produced with the pattern of FIG. 1.

(14) Once the knit is produced, it is cut along the warp direction on both sides of the weft stitched chain stitches 6 along cutting lines 11 as shown on FIG. 3. The cutting step may be performed for example with a pair of scissors.

(15) An isolated weft stitched chain stitch 6, in which the chain stitch yarn 1 of the weft stitched chain stitch 6 forms the elongate body 9 of a barbed suture 10 and the monofilament cuts 7 extending from the weft stitches 5 of the weft stitched chain stitch 6 form the barbs 8 of the barbed suture 10 is obtained, as shown on FIG. 4. As shown on this Figure, the weft stitched chain stitch 6 which is also the elongate body 9 of the suture 10 extends along a longitudinal axis A1, and the monofilament cuts 7, which are also the barbs 8, each extend along a longitudinal axis A2. On FIG. 4, which shows the isolated weft stitched chain stitch 6 right after the cutting step, the angle between axis A1 and axis A2 is substantially about 90.

(16) As appears from the cutting step shown on FIG. 3, the length of the monofilament cuts 7, and therefore of the barbs 8, depend both on the initial distance between the weft stitched chain stitch 6 and adjacent chain stitches 3, and on the location of the cutting lines 11.

(17) With reference to FIG. 6 is shown schematically a barbed suture 10 obtained according to the method of the present example in the case where the second guide bar B2 was fed intermittently with the set of monofilament weft yarns. During the time periods for which the guide bar B2 was not fed with the monofilament weft yarns, no weft stitches were produced on the weft stitched chain stitch 6, thereby resulting in portions of the weft stitched chain stitch 6 free of barbs, namely passive portions 13. A barbed suture 10 having alternating active portions 14 (when guide bar B2 was fed with monofilament wefts yarns) and passive portions 13 is therefore be obtained. As shown on this Figure, the respective distances (L1, L2) between two adjacent active portions 14 may vary, as such distances are dependent on the time period during which the guide bar B2 was not fed.

(18) With reference to FIG. 5 is shown a larger view of the barbed suture 10 of FIG. 4 after a stretching treatment in which the barbed suture was stretched at 90%. As appears from this Figure, after the stretching treatment, the angle between between axis A1 and axis A2, in other words between the multifilament yarn 1 forming the elongate body 9 of the barbed suture 10 and the monofilament cuts 7, also barbs 8, has been modified and is now about 33.

(19) The barbed suture 10 of FIG. 5 is then submitted to a heat-setting treatment in order to fix the configuration of the barbs 8 with respect to the elongate body 9 of the suture 10.

(20) In embodiments not shown, the knitting pattern may result in all chain stitches being also weft stitched chain stitches, when the weft yarns produce weft stitches with all chain stitches produced by the first guide bar. In other embodiments, the knitting pattern may produce only one weft stitched chain stitch out of three, four, five, etc . . . chain stitches present in the knit, which may result in variations of the distance between two adjacent weft stitched chain stitches. Alternatively, this distance may vary due to different threading-in of the guide bars.

Example 2

(21) In this example is described an alternative knitting pattern to Example 1 for producing a barbed suture of the invention.

(22) A knit is produced on a raschel machine wherein the knitting pattern followed by bars B1 and B2 is the following according to the ISO 11676 standard: Bar B1: 0.1/1.0// Bar B2: 9.9/5.4/0.0/0.0/4.5/9.9//

(23) wherein B1 is threaded 1 full, 3 empty, and B2 is threaded 1 full, 7 empty.

(24) The yarns threaded in guide bar Bar 1 are multifilament yarns of ultra high molecular weight polyethylene, such as those marketed by the company DSM under the tradename Dyneema Purity. These multifilaments have a tensile strength of 35 cN/dTex.

(25) The monofilaments threaded in guide bar Bar 2 are polypropylene monofilaments having a diameter of 0.25 mm.

(26) With reference to FIG. 2 showing the knitting pattern, are shown the chain stitch yarns 1 (threaded in guide bar B1) and the monofilament weft yarns 2 (threaded in guide bar B2). The knitting pattern produces a plurality of chain stitches 3 and a partial weft 4. The weft yarns 2 complete weft stitches 5 with some of the chain stitches 3, herein after called weft stitched chain stitches 6. Actually, as appears from FIG. 2, the knitting pattern produces one weft stitched chain stitch 6 out of two chain stitches 3 present in the knit. In the present example, the distance between two adjacent weft stitched chain stitches 6 is due to the threading-in of the first guide bar B1, which is 1 full, 3 empty. Such a threading-in may result in a distance between the weft stitched chain stitches 6 of about 0.5 cm.

(27) Once the knit is produced, it is cut as described in Example 1 to obtain an isolated weft stitched chain stitch 6.

(28) The isolated weft stitched chain stitch 6 may then be stretched, and/or twisted in order to put the monofilaments cuts 7, also barbs 8, in a desired configuration, and eventually heat-set in order to fix said configuration to obtain a barbed suture 10 of the invention.

(29) The method of the invention allows adapting very easily and in a cost effective manner the nature and structure of the barbed suture, such as frequency per cm, configuration, spacing, length and surface area of the barbs, depending upon the tissue in which the barbed suture is to be used. With the method of the invention, it is possible to obtain a barbed suture in which the barbs may be arranged in any suitable pattern, for example, helical, linear, or randomly spaced. In addition, the method of the invention allows producing a high amount of barbed suture in a cost effective way and at high production rates.