SUTURE THREAD PRODUCTS

Abstract

There is provided a product comprising a suture thread which, prior to being used to form a surgical suture, is in a stressed state which gives the suture thread a tendency to undergo lengthwise viscoelastic contraction. The suture thread undergoes viscoelastic contraction when in use as a surgical suture and this may promote wound healing to a greater extent than a conventional suture thread which does not undergo viscoelastic contraction.

Claims

1. A method of manufacturing a product comprising a suture thread, the method comprising: providing a thread having a length; applying to the thread a stressed state which gives the thread a tendency to undergo lengthwise viscoelastic contraction; and after said application of the stressed state, engaging at least part of the length of the thread with a structure to form an engaged suture thread, said engagement with the structure maintaining the thread in a stressed state by resisting lengthwise viscoelastic contraction of the thread by application of a force to the thread, the structure being disengageable from the thread to allow lengthwise viscoelastic contraction of the thread when it is desired to use the suture to form a surgical suture.

2. The method according to claim 1, wherein said engaging comprises winding said at least part of the length of the thread around a portion of the structure and securing two ends of said at least part of the length of the thread to the structure.

3. The method according to claim 1, wherein the engaged thread is packed in a package wherein the package is suitable for maintaining sterility of the thread.

4. The method according to 1, wherein said engaging comprises engaging part of the length of the thread with the structure and the thread is cut to form said part of the length after said application of the stressed state.

5. The method according to 1, further comprising sterilizing the thread.

6. The method according to 1, wherein said application of said stressed state comprises applying a tensile force to the thread so that the thread undergoes lengthwise viscoelastic creep.

7. The method according to claim 6, wherein said application of said stressed state further comprises, after the thread has undergone said viscoelastic creep, releasing the tensile force and allowing the thread to undergo elastic contraction.

8. The method according to claim 1, further comprising refrigerating the thread in a package.

9. A method of manufacturing a suture thread, the method comprising: configuring a thread to have a stressed state of lengthwise viscoelastic contraction; engaging at least part of a length of the thread with a structure, said engagement with the structure substantially maintaining the thread in the stressed state by resisting lengthwise viscoelastic contraction of the suture thread; and disengaging the structure from the thread to allow lengthwise viscoelastic contraction of the suture thread to use the thread to form a surgical suture.

10. The method according to claim 9, wherein the engaging comprises winding the at least part of the length of the thread around a portion of the structure.

11. The method according to claim 10, further comprising securing at least one end of the at least part of the length of the thread to the structure.

12. The method according to claim 9, wherein the engaging comprises cutting the thread to form the part of the length while the thread is in the stressed state.

13. The method according to claim 9, further comprising sterilizing the thread.

14. The method according to claim 13, further comprising packing the engaged thread in a package.

15. The method according to claim 14, further comprising cooling the package.

16. A method of manufacturing a suture thread, the method comprising: applying a tensile force to a thread so that the thread undergoes lengthwise viscoelastic creep; allowing the thread to undergo elastic contraction resulting in the thread being in a stressed state; and engaging at least part of the thread with a structure so as to substantially maintain the thread in the stressed state until the structure is disengaged from the thread.

17. The method according to claim 16, wherein the engaging comprises winding at least a part of the thread around a portion of the structure and securing at least one end of the thread to the structure.

Description

[0053] The following is a more detailed description, by way of example, of the preparation of suture threads which are in a stressed state so as to give the suture threads a tendency to undergo lengthwise viscoelastic contraction and of the manufacture of products comprising the threads, reference being made to the drawings in which:

[0054] FIG. 1 is a graph showing viscoelastic contraction of a first suture thread;

[0055] FIG. 2 is a graph showing viscoelastic contraction of second and third suture threads;

[0056] FIG. 3a is a photograph of a water droplet on a suture thread formed from nylon 6,6 which is in a stressed state so as to give the suture thread a tendency to undergo lengthwise viscoelastic contraction (the suture thread of FIG. 1);

[0057] FIG. 3b is a photograph of a water droplet on a thread formed from nylon 6,6 which is not in a stressed state;

[0058] FIG. 4 is a graph showing force generated over time by a suture thread undergoing lengthwise viscoelastic contraction; and

[0059] FIG. 5 is a schematic drawing of a suture thread engaged with a spool which maintains the suture thread in a stressed state.

EXAMPLE 1

[0060] This example describes the manufacture of a first suture thread and the lengthwise viscoelastic contraction that is undergone by the first suture thread.

[0061] The first suture thread was manufactured from a nylon 6,6 monofilament thread having a diameter of 1.6 mm. The manufacture process consisted of: first subjecting the nylon 6,6 thread to a heat treatment; then subjecting it to a tensile force to cause viscoelastic creep; and finally releasing the tensile force to allow the thread to undergo elastic contraction so as to leave the thread in a stressed state with a tendency to undergo viscoelastic contraction.

[0062] The heat treatment (or annealing) was performed at a temperature of 150° C. for 30 minutes after which the thread was allowed to cool to ambient temperature.

[0063] The thread was then subjected to a tensile stress of 55 MPa for 20 hours at a temperature of 20° C. to 22° C. After this time, the thread had undergone viscoelastic creep so as to extend by 10.10% as a percentage of the initial thread length (i.e. final creep strain=10.10%).

[0064] Finally, the tensile force was released and the thread underwent elastic contraction, after which the remaining extension, as a percentage of the initial thread length, was approximately 7.2%.

[0065] As will be seen from FIG. 1, the first suture thread manufactured as described above, when left without application of force, at 20° C. to 21° C., underwent a degree of viscoelastic contraction of 5%-6% over a period of 1000 hours (equivalent to about 6 weeks). The degree of viscoelastic contraction is expressed as a percentage of the length of the suture thread (after manufacture as described above) and not as a percentage of the initial length of the thread used to manufacture the suture thread.

[0066] It will be appreciated that after manufacture of the suture thread, the suture thread may be packaged in a package as described above. Alternatively, or in addition, the suture thread may be engaged with a structure that maintains the tendency to undergo viscoelastic contraction, as described above. Both the suture thread and the structure may be packaged in a package. Alternatively, the structure may be part of a package.

EXAMPLE 2

[0067] This example describes the manufacture of second and third suture threads and the lengthwise viscoelastic contraction that is undergone by the second and third suture threads.

[0068] The second suture thread according to the invention was manufactured from a polypropylene monofilament thread having a diameter of 0.3 mm, and sold by Ethicon US, LLC as Prolene (trade mark) EH7779 Blue Suture. The manufacture process consisted of first subjecting the polypropylene thread to a heat treatment; then subjecting it to a tensile force to cause viscoelastic creep; and finally releasing the tensile force to allow the thread to undergo elastic contraction so as to leave the thread in a stressed state with a tendency to undergo viscoelastic contraction.

[0069] The heat treatment (or annealing) was performed at a temperature of 120° C. for 30 minutes after which the thread was allowed to cool to ambient temperature.

[0070] The thread was then subjected to a tensile stress of 135.3 MPa for 24 hours at a temperature of 20° C. to 21° C. After this time, the thread had undergone viscoelastic creep so as to extend by 17. 2% as a percentage of the initial thread length (i.e. final creep strain=17.2%).

[0071] Finally, the tensile force was released and the thread underwent elastic contraction, after which the remaining extension, as a percentage of the initial thread length, was approximately 9.4%.

[0072] Viscoelastic contraction of the second suture thread is shown in FIG. 2 as Run 1. The second suture thread manufactured as described above, when left without application of force, at 20° C. to 21° C., underwent a degree of viscoelastic contraction of about 3.4% over a period of 1000 hours (equivalent to about 6 weeks). The degree of viscoelastic contraction is expressed as a percentage of the length of the suture thread (after manufacture as described above) and not as a percentage of the initial length of the thread used to manufacture the suture thread.

[0073] The third suture thread was manufactured from an identical polypropylene monofilament thread using a similar method to that described above in respect of the second suture thread. The only differences in the manufacture of the third suture thread were that the heat treatment (or annealing) was performed at a temperature of 120° C. for 8 hours (instead of 30 minutes) and that the polypropylene monofilament thread was then subjected to a tensile stress of 135.3 MPa for 48 hours (instead of 24 hours) at a temperature of 20° C. to 21° C. After this time, the thread had undergone viscoelastic creep so as to extend by 20.5% as a percentage of the initial thread length (i.e. final creep strain=20.5%).

[0074] The tensile force was then released and the thread underwent elastic contraction, after which the remaining extension, as a percentage of the initial thread length, was approximately 13.1%.

[0075] Viscoelastic contraction of the third suture thread is shown in FIG. 2 as Run 2. The third suture thread manufactured as described above, when left without application of force, at 20° C. to 21° C., underwent a degree of viscoelastic contraction of about 5.0% over a period of 1000 hours (equivalent to about 6 weeks). The degree of viscoelastic contraction is expressed as a percentage of the length of the suture thread (after manufacture as described above) and not as a percentage of the initial length of the thread used to manufacture the suture thread.

[0076] It will be appreciated that after manufacture of either the second or third suture thread, the suture thread may be packaged in a package as described above. Alternatively, or in addition, the suture thread may be engaged with a structure that maintains the tendency to undergo viscoelastic contraction, as described above. Both the suture thread and the structure may be packaged in a package. Alternatively, the structure may be part of a package.

EXAMPLE 3

[0077] This example describes how the application of the stressed state appears to change the surface characteristics of the suture thread according to the invention.

[0078] FIG. 3a shows a nylon 6,6 suture thread prepared under the same conditions as used in Example 1 above, after relaxation of the elastic extension but before extensive viscoelastic contraction had occurred.

[0079] FIG. 3b shows a comparative nylon 6,6 thread (1.6 mm diameter monofilament) but which had not been subjected to viscoelastic creep.

[0080] FIGS. 3a and 3b show single water droplets on the respective nylon threads. The contact angle between the suture thread to which a stressed state had been applied as per Example 1 and its water droplet (FIG. 3a) was lower than the contact angle between the comparative nylon 6,6 thread and its water droplet (FIG. 3b). This suggests that the treatment used to apply the state of stress, and the tendency to undergo viscoelastic contraction, results in a modest decrease in the surface hydrophobicity.

EXAMPLE 4

[0081] This Example demonstrates the capacity of the suture threads to apply a force as they undergo viscoelastic contraction.

[0082] A suture thread was formed into a loop by attaching the two ends to one another, having an overall (circular) length of about 60 cm. The heat treatment (or annealing) and tensile stress conditions were identical to the third suture thread described above. The loop was then placed around both a fixed support and the measurement point of a force gauge so that the loop was positioned, without appreciable tautness, between the fixed support and the attachment point. Force generated by the loop was measured over time at 20-21° C. The viscoelastic contraction of the loop was generally equivalent to the viscoelastic contraction of two lengths of suture thread, arranged in parallel to one another and each having a length approximately half that of the loop. The force was generated at a constant strain of 12% (as the fixed support and the attachment point of the force gauge were held substantially immobile relative to one another). It is believed that the length of the suture thread is not a major factor in the magnitude of the force. The results are shown in FIG. 4. As seen in FIG. 4, the generated force increased in a time dependent manner with the rate of increase of the force decreasing with time. After 100 hours the applied force was about 2.2N.

EXAMPLE 5

[0083] This example demonstrates the use of a structure to maintain the stressed state of the suture thread.

[0084] In this example, the structure is a simple spool 10. The suture thread 12 is wound around the spool 10 after the application of the stressed state. The two ends 14 of the suture thread are passed through a slot 16 in the spool 10. Each end 14 of the suture thread 12 is then knotted so as to fix the ends 14 to the spool 10 so that the spool 10 resists lengthwise viscoelastic contraction of the suture thread 12.