LASER CUTTING SYSTEM AND METHODS FOR CREATING SELF-RETAINING SUTURES
A laser-machining system and method is disclosed for forming retainers on a suture thread. The laser system is preferably a femtosecond laser system which is capable of creating submicron features on the suture thread while preserving strength of the suture thread. The laser-machining system enables creation of retainers and self-retaining suture systems in configurations which are difficult and/or impossible to achieve using mechanical cutting technology.
1 . A method for making a self-retaining suture comprising;
(a) providing a suture thread having a surface;
(b) identifying a first volume of suture material on the surface of the thread;
(c) identifying a second volume of suture material from within the first volume of suture material;
(d) directing a laser beam at the suture thread to ablate all of the suture material within the first volume of suture material with the exception of the second volume of suture material whereby the second volume of suture material forms a tissue retainer protruding from laser cut surface of the suture thread; and
(e) repeating steps (b), (c) and (d) to generate a plurality of tissue retainers protruding from the suture thread.
2 . The method of claim 1 , wherein step (c) comprises identifying a second volume of suture material from within the first volume of suture material the second volume being less than 50% of the first volume.
3 . The method of claim 1 , wherein step (c) comprises identifying a second volume of suture material from within the first volume of suture material the second volume being less than 25% of the first volume.
4 . The method of claim 1 , wherein:
step (c) comprises identifying a conical subvolume of suture material from within the volume of suture material wherein the subvolume of suture material; and
step (d) comprises directing a laser beam at the suture thread to ablate all of the suture material within the selected volume of suture material with the exception of the conical subvolume of suture material whereby the conical subvolume of suture material forms a tissue retainer protruding from laser cut surface of the suture thread.
5 . The method of claim 1 , wherein step (a) comprises providing a suture thread having a surface and a noncircular cross-section.
6 . The method of claim 1 , wherein:
step (a) comprises providing a suture thread having a surface and a plurality of longitudinal ridges noncircular cross-section; and
step (b) comprises identifying a first volume of suture material on the surface of the thread within one of the longitudinal ridges.
7 . The method of claim 1 , wherein:
step (a) comprises providing a suture thread having a surface and a polygonal cross section having a plurality of longitudinal apices; and
step (b) comprises identifying a first volume of suture material on the surface of the thread including one of the longitudinal apices.
8 . A method for making a self-retaining suture comprising;
(a) identifying a tissue retainer location on the suture thread;
(b) directing a laser beam at the tissue retainer location on the suture thread;
(c) using the laser beam to remove a volume of material defining a slot from said suture thread, wherein the slot defines a tissue engagement surface of a tissue retainer;
(d) repeating steps (a), (b) and (c) to generate a plurality of tissue retainers on the suture thread.
9 . The method of claim 8 , wherein step (c) comprises
(c1) using the laser beam to remove a volume of material defining a slot from said suture thread, wherein the slot defines a tissue engagement surface of a tissue retainer; and
(c2) using the laser beam to remove a wedge-shaped volume of material from said suture thread adjacent the slot to provide an entrance ramp which promotes engagement of tissue by said tissue engagement surface.
10 . The method of claim 8 , wherein step (b) comprises directing a laser beam at the tissue retainer location on the suture thread and focusing the laser beam to a diameter no greater than 5 nm.
11 . The method of claim 8 , wherein step (b) comprises directing a femtosecond laser beam at the tissue retainer location on the suture thread.
12 . The method of claim 8 , further comprising:
(e) after completion of step (d), treating the suture thread to cause a tip of each of said plurality of retainers to elevate above a surface of said suture thread.
13 . The method of claim 8 , further comprising:
(e) after completion of step (d) treating the suture thread to cause a tip of each of said plurality of retainers to elevate above a surface of said suture thread; and
(f) annealing the suture thread to cause a tip of each of said plurality of retainers to remain elevated above the surface of said suture thread.
14 . A laser-machining system adapted to make tissue retainers on a suture thread, wherein the laser-machining system comprises:
a laser subsystem adapted to provide a laser beam;
an optic system adapted to receive the laser beam and generate a focused laser beam directed at a volume of the suture thread;
a transport subsystem adapted to move the suture thread relative to the laser beam;
an imaging subsystem adapted to image the suture thread and generate image data; and
a control subsystem adapted to receive said image data from the laser subsystem and transport subsystem to create a tissue retainer of a selected configuration at a selected location on said suture thread.
15 . The laser-machining system of claim 14 , wherein:
the laser subsystem comprises a femtosecond laser.
16 . The laser-machining system of claim 14 , wherein:
the control subsystem provides focus control signals to the optical subsystem in response to the image data; and
the optic subsystem is adapted to change the focus depth of the laser beam in response to the focus control signals.
17 . The laser-machining system of claim 14 further comprising an air bearing device which provides a high speed laminar flow of fluid along and surrounding the suture thread at the selected location.
18 . The laser-machining system of claim 14 , wherein;
the optic subsystem includes one or more axicon prisms.
19 . The laser-machining system of claim 14 , wherein:
the laser beam has a ring-shaped power density distribution of selectable ring diameter.
20 . A stabilization device for contactless stabilization of a suture thread in a region of the suture thread, wherein the stabilization device comprises:
a source of pressurized fluid; and
a fluid outlet connected to the source of pressurized fluid and adapted to generate a laminar flow of fluid along the suture thread and surrounding the suture thread in the region of the suture thread.
21 . The stabilization device of claim 20 , wherein the stabilization device comprises:
a fluid manifold wherein the fluid manifold is connected to the source of pressurized fluid and the fluid outlet is connected to one end of the fluid manifold;
a suture inlet connected to the fluid manifold; and
wherein the stabilization device is configured such that a suture thread can enter the fluid manifold through an entry port and leave the fluid manifold through the fluid outlet without contacting the entry port and fluid outlet.
22 . A method for creating a self-retaining suture comprising:
(a) positioning a selected region of the suture thread in a laminar flow of fluid adapted to stabilize the position of the selected region of the suture thread;
(b) directing a laser beam at a selected volume of suture material within the selected region of the suture thread;
(c) removing the selected volume of the suture material from within the selected region of the suture thread to create a tissue retainer;
(d) repeating steps (a), (b) and (c) for a plurality of selected regions of the suture thread to create a plurality of tissue retainers.
23 . The method of claim 22 , further comprising:
(e) positioning a selected marking region of the suture thread in the laminar flow of fluid and directing electromagnetic radiation at the suture thread within the selected marking region wherein the electromagnetic radiation is adapted to change a visual characteristic of the selected marking region of the suture thread without ablating suture material.
24 . A method for making a self-retaining suture comprising;
(a) identifying a tissue retainer location on the suture thread;
(b) providing a laser beam;
(b) directing a laser beam at a portion of the tissue retainer location on the suture thread;
(c) using the laser beam to remove a volume of suture material from the tissue retainer location on the suture thread to create a tissue retainer having a tip;
(d) repeating steps (a), (b) and (c) to generate a plurality of tissue retainers on the suture thread; and
(e) subsequent to step (d) treating the self-retaining suture to elevate the tips of the plurality of tissue retainers so that the tips protrude from the suture thread.
25 . The method of claim 24 , further comprising:
(f) subsequent to step (e) annealing the self-retaining suture to maintain the tips of the plurality of tissue retainers so that the tips protrude from the suture thread.