U.S. patent application number 13/695112 was filed with the patent office on 2013-07-18 for laser cutting system and methods for creating self-retaining sutures.
The applicant listed for this patent is Jacob D. Conner, William L. D'Agostino, Fred M. Dickey, Lev Drubetsky, Jeffrey M. Gross, Alexander Naimagon, Kevin R. Whitworth, Ryan T. Woolsey. Invention is credited to Jacob D. Conner, William L. D'Agostino, Fred M. Dickey, Lev Drubetsky, Jeffrey M. Gross, Alexander Naimagon, Kevin R. Whitworth, Ryan T. Woolsey.
Application Number | 20130180966 13/695112 |
Document ID | / |
Family ID | 44904466 |
Filed Date | 2013-07-18 |
United States Patent
Application |
20130180966 |
Kind Code |
A1 |
Gross; Jeffrey M. ; et
al. |
July 18, 2013 |
LASER CUTTING SYSTEM AND METHODS FOR CREATING SELF-RETAINING
SUTURES
Abstract
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.
Inventors: |
Gross; Jeffrey M.;
(Vancouver, CA) ; D'Agostino; William L.; (Hamden,
CT) ; Drubetsky; Lev; (Coquitlam, CA) ;
Naimagon; Alexander; (Richmond, CA) ; Conner; Jacob
D.; (Springfield, MO) ; Whitworth; Kevin R.;
(Springfield, MO) ; Woolsey; Ryan T.;
(Springfield, MO) ; Dickey; Fred M.; (Springfield,
MO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Gross; Jeffrey M.
D'Agostino; William L.
Drubetsky; Lev
Naimagon; Alexander
Conner; Jacob D.
Whitworth; Kevin R.
Woolsey; Ryan T.
Dickey; Fred M. |
Vancouver
Hamden
Coquitlam
Richmond
Springfield
Springfield
Springfield
Springfield |
CT
MO
MO
MO
MO |
CA
US
CA
CA
US
US
US
US |
|
|
Family ID: |
44904466 |
Appl. No.: |
13/695112 |
Filed: |
May 4, 2011 |
PCT Filed: |
May 4, 2011 |
PCT NO: |
PCT/US2011/035270 |
371 Date: |
March 12, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61331302 |
May 4, 2010 |
|
|
|
61331294 |
May 4, 2010 |
|
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Current U.S.
Class: |
219/121.69 ;
219/121.68; 269/20 |
Current CPC
Class: |
A61B 17/0644 20130101;
A61B 2017/0417 20130101; A61B 2017/00526 20130101; B23K 26/361
20151001; B23K 26/0652 20130101; B23K 26/0665 20130101; A61B
2017/0427 20130101; B23K 26/362 20130101; A61B 2090/3937 20160201;
B23K 37/04 20130101; A61B 2017/06176 20130101; B23K 26/083
20130101; A61B 17/0401 20130101; A61B 17/06166 20130101; B23K
26/032 20130101; A61B 2017/06038 20130101; B23K 26/1462
20151001 |
Class at
Publication: |
219/121.69 ;
219/121.68; 269/20 |
International
Class: |
B23K 26/36 20060101
B23K026/36; B23K 26/08 20060101 B23K026/08; B23K 26/14 20060101
B23K026/14; B23K 26/06 20060101 B23K026/06 |
Claims
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.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a National Stage application under 35
U.S.C. 371 of PCT/US2011/035270, filed on May 4, 2011, which claims
priority from U.S. Provisional Application Ser. No. 61/331,294,
filed on May 4, 2010 and U.S. Provisional Application Ser. No.
61/331,302, filed on May 4, 2010.
FIELD OF INVENTION
[0002] The present invention relates generally to laser-cutting
equipment and methods of manufacturing self-retaining suture
systems for surgical procedures.
BACKGROUND OF INVENTION
[0003] Wound closure devices such as sutures, staples and tacks
have been widely used in superficial and deep surgical procedures
in humans and animals for closing wounds, repairing traumatic
injuries or defects, joining tissues together (bringing severed
tissues into approximation, closing an anatomical space, affixing
single or multiple tissue layers together, creating an anastomosis
between two hollow/luminal structures, adjoining tissues, attaching
or reattaching tissues to their proper anatomical location),
attaching foreign elements to tissues (affixing medical implants,
devices, prostheses and other functional or supportive devices),
and for repositioning tissues to new anatomical locations (repairs,
tissue elevations, tissue grafting and related procedures) to name
but a few examples.
[0004] Sutures are often used as wound closure devices. Sutures
typically consist of a filamentous suture thread attached to a
needle with a sharp point. Suture threads can be made from a wide
variety of materials including bioabsorbable (i.e., that break down
completely in the body over time), or non-absorbable (permanent;
non-degradable) materials. Absorbable sutures have been found to be
particularly useful in situations where suture removal might
jeopardize the repair or where the natural healing process renders
the support provided by the suture material unnecessary after wound
healing has been completed; as in, for example, completing an
uncomplicated skin closure. Non-degradable (non-absorbable) sutures
are used in wounds where healing may be expected to be protracted
or where the suture material is needed to provide physical support
to the wound for long periods of time; as in, for example, deep
tissue repairs, high tension wounds, many orthopedic repairs and
some types of surgical anastomosis. Also, a wide variety of
surgical needles are available; the shape and size of the needle
body and the configuration of the needle tip is typically selected
based upon the needs of the particular application.
[0005] To use an ordinary suture, the suture needle is advanced
through the desired tissue on one side of the wound and then
through the adjacent side of the wound. The suture is then formed
into a "loop" which is completed by tying a knot in the suture to
hold the wound closed. Knot tying takes time and causes a range of
complications, including, but not limited to (i) spitting (a
condition where the suture, usually a knot) pushes through the skin
after a subcutaneous closure), (ii) infection (bacteria are often
able to attach and grow in the spaces created by a knot), (iii)
bulk/mass (a significant amount of suture material left in a wound
is the portion that comprises the knot), (iv) slippage (knots can
slip or come untied), and (v) irritation (knots serve as a bulk
"foreign body" in a wound). Suture loops associated with knot tying
may lead to ischemia (knots can create tension points that can
strangulate tissue and limit blood flow to the region) and
increased risk of dehiscence or rupture at the surgical wound. Knot
tying is also labor intensive and can comprise a significant
percentage of the time spent closing a surgical wound. Additional
operative procedure time is not only bad for the patient
(complication rates rise with time spent under anesthesia), but it
also adds to the overall cost of the operation (many surgical
procedures are estimated to cost between $15 and $30 per minute of
operating time).
[0006] Self-retaining sutures (including barbed sutures) differ
from conventional sutures in that self-retaining sutures possess
numerous tissue retainers (such as barbs) which anchor the
self-retaining suture into the tissue following deployment and
resist movement of the suture in a direction opposite to that in
which the retainers face, thereby eliminating the need to tie knots
to affix adjacent tissues together (a "knotless" closure). Knotless
tissue-approximating devices having barbs have been previously
described in, for example, U.S. Pat. No. 5,374,268, disclosing
armed anchors having barb-like projections, while suture assemblies
having barbed lateral members have been described in U.S. Pat. Nos.
5,584,859 and 6,264,675. Sutures having a plurality of barbs
positioned along a greater portion of the suture are described in
U.S. Pat No. 5,931,855, which discloses a unidirectional barbed
suture, and U.S. Pat. No. 6,241,747, which discloses a
bidirectional barbed suture. Methods and apparatus for forming
barbs on sutures have been described in, for example, U.S. Pat. No.
6,848,152. Self-retaining systems for wound closure also result in
better approximation of the wound edges, evenly distribute the
tension along the length of the wound (reducing areas of tension
that can break or lead to ischemia), decrease the bulk of suture
material remaining in the wound (by eliminating knots) and reduce
spitting (the extrusion of suture material--typically
knots--through the surface of the skin. All of these features are
thought to reduce scarring, improve cosmesis, and increase wound
strength relative to wound closures using plain sutures or staples.
Thus, self-retaining sutures, because such sutures avoid knot
tying, allow patients to experience an improved clinical outcome,
and also save time and costs associated with extended surgeries and
follow-up treatments. It is noted that all patents, patent
applications and patent publications identified throughout are
incorporated herein by reference in their entirety.
[0007] The ability of self-retaining sutures to anchor and hold
tissues in place even in the absence of tension applied to the
suture by a knot is a feature that also provides superiority over
plain sutures. When closing a wound that is under tension, this
advantage manifests itself in several ways: (i) self-retaining
sutures have a multiplicity of retainers which can dissipate
tension along the entire length of the suture (providing hundreds
of "anchor" points this produces a superior cosmetic result and
lessens the chance that the suture will "slip" or pull through) as
opposed to knotted interrupted sutures which concentrate the
tension at discrete points; (ii) complicated wound geometries can
be closed (circles, arcs, jagged edges) in a uniform manner with
more precision and accuracy than can be achieved with interrupted
sutures; (iii) self-retaining sutures eliminate the need for a
"third hand" which is often required for maintaining tension across
the wound during traditional suturing and knot tying (to prevent
"slippage" when tension is momentarily released during tying); (iv)
self-retaining sutures are superior in procedures where knot tying
is technically difficult, such as in deep wounds or
laparoscopic/endoscopic procedures; and (v) self-retaining sutures
can be used to approximate and hold the wound prior to definitive
closure. As a result, self-retaining sutures provide easier
handling in anatomically tight or deep places (such as the pelvis,
abdomen and thorax) and make it easier to approximate tissues in
laparoscopic/endoscopic and minimally invasive procedures; all
without having to secure the closure via a knot. Greater accuracy
allows self-retaining sutures to be used for more complex closures
(such as those with diameter mismatches, larger defects or purse
string suturing) than can be accomplished with plain sutures.
[0008] A self-retaining suture may be unidirectional, having one or
more retainers oriented in one direction along the length of the
suture thread; or bidirectional, typically having one or more
retainers oriented in one direction along a portion of the thread,
followed by one or more retainers oriented in another (often
opposite) direction over a different portion of the thread (as
described with barbed retainers in U.S. Pat. Nos. 5,931,855 and
6,241,747). Although any number of sequential or intermittent
configurations of retainers are possible, one form of
unidirectional self-retaining suture includes a tissue anchor on
the distal end and a needle on the proximal end and a plurality of
barbs on the surface of the suture thread having tips projecting
"away" from the needle. Projecting "away" from the needle means
that the tip of the barb is further away from the needle and the
portion of suture comprising the barb may be pulled more easily
through tissue in the direction of the needle than in the opposite
direction (towards the tissue anchor). The tissue anchor is
designed to secure the distal end of the suture and includes in
some embodiments a loop, staple, tack, bar, plug, sheet, or
ball.
[0009] Although any number of sequential or intermittent
configurations of retainers are possible, one form of bidirectional
self-retaining suture includes a needle at one end of a suture
thread which has barbs having tips projecting "away" from the
needle until the transition point (often the midpoint) of the
suture is reached; at the transition point the configuration of
barbs reverses itself about 180.degree. (such that the barbs are
now facing in the opposite direction) along the remaining length of
the suture thread before attaching to a second needle at the
opposite end (with the result that the barbs on this portion of the
suture also have tips projecting "away" from the nearest needle).
Put another way, the barbs on both "halves" of a typical
bidirectional self-retaining suture have tips that point towards
the middle, with a transition segment (lacking barbs) interspersed
between them, and with a needle attached to either end.
SUMMARY OF INVENTION
[0010] Despite the multitude of advantages of unidirectional and
bidirectional self-retaining sutures, there remains a need to
improve upon the design of the suture such that a variety of
limitations can be eliminated and enhanced and/or additional
functionality is provided.
[0011] In accordance one aspect, the present invention provides
laser cutting apparatus for creating retainers on a suture
thread.
[0012] In accordance with another aspect, the present invention
provides apparatus for stabilizing a suture during laser-cutting of
retainers.
[0013] In accordance with another aspect, the present invention
provides methods for cutting retainers on a suture thread with a
laser.
[0014] The details of one or more embodiments are set forth in the
description below. Other features, objects and advantages will be
apparent from the description, the drawings, and the claims. In
addition, the disclosures of all patents and patent applications
referenced herein are incorporated by reference in their entirety.
For example, this application incorporates by reference U.S.
application Ser. No. ______, filed ______, (Attorney Reference No.
2284.40854USPC), which is the U.S. National Phase of International
Application No. ______ filed May 4, 2011, entitled SELF-RETAINING
SYSTEM HAVING LASER-CUT RETAINERS (Attorney Reference No.
2284.40854PC).
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Features of the invention, its nature and various advantages
will be apparent from the accompanying drawings and the following
detailed description of various embodiments.
[0016] FIG. 1A is a perspective view of a bidirectional
self-retaining suture.
[0017] FIGS. 1B-1D are enlarged views of portions of the suture of
FIG. 1A.
[0018] FIG. 1E is a perspective view of a unidirectional
self-retaining suture.
[0019] FIGS. 1F-1H are views of alternative tissue anchors for the
unidirectional self-retaining suture of FIG. 1E.
[0020] FIG. 2A shows a schematic diagram of a laser-machining
system suitable for forming retainers on a suture thread according
to an embodiment of the present invention.
[0021] FIG. 2B is an image of a Gaussian laser beam.
[0022] FIG. 2C is a graphical representation of the power density
distribution in a Gaussian laser beam.
[0023] FIG. 2D is an image of a laser beam from an axicon prism
system.
[0024] FIG. 2E is a graphical representation of the power density
distribution in a laser beam from an axicon prism system.
[0025] FIG. 3A shows a sectional view of an air bearing for use in
the laser-machining system of FIG. 2 according to an embodiment of
the present invention.
[0026] FIG. 3B shows a partial perspective view of the air bearing
of FIG. 3A.
[0027] FIG. 4A is a flow chart of a method for creating a
self-retaining suture utilizing the laser-machining system of FIG.
2 according to an embodiment of the present invention.
[0028] FIGS. 4B-4D are perspective views of a suture filament
during the process of generating a laser-cut retainer utilizing the
laser-machining system of FIG. 2 according to an embodiment of the
present invention.
[0029] FIG. 5 is an image of a laser-cut surface of a
self-retaining suture.
[0030] FIG. 6 is a graph showing the profile of the laser-cut
surface of FIG. 5.
[0031] FIG. 7 shows a retainer distribution configurations for a
self-retaining suture made utilizing the laser-machining system of
FIG. 2.
[0032] FIGS. 8A-8F show examples of self-retaining sutures made
utilizing the laser-machining system of FIG. 2.
DETAILED DESCRIPTION
Definitions
[0033] Definitions of certain terms that may be used hereinafter
include the following.
[0034] "Self-retaining system" refers to a self-retaining suture
together with devices for deploying the suture into tissue. Such
deployment devices include, without limitation, suture needles and
other deployment devices as well as sufficiently rigid and sharp
ends on the suture itself to penetrate tissue.
[0035] "Self-retaining suture" refers to a suture that comprises
features on the suture filament for engaging tissue without the
need for a knot or suture anchor.
[0036] "Tissue retainer" (or simply "retainer") or "barb" refers to
a physical feature of a suture filament which is adapted to
mechanically engage tissue and resist movement of the suture in at
least one axial directions. By way of example only, tissue retainer
or retainers can include hooks, projections, barbs, darts,
extensions, bulges, anchors, protuberances, spurs, bumps, points,
cogs, tissue engagers, traction devices, surface roughness, surface
irregularities, surface defects, edges, facets and the like. In
certain configurations, tissue retainers are adapted to engage
tissue to resist movement of the suture in a direction other than
the direction in which the suture is deployed into the tissue by
the physician, by being oriented to substantially face the
deployment direction. In some embodiments the retainers lie flat
when pulled in the deployment direction and open or "fan out" when
pulled in a direction contrary to the deployment direction. As the
tissue-penetrating end of each retainer faces away from the
deployment direction when moving through tissue during deployment,
the tissue retainers should not catch or grab tissue during this
phase. Once the self-retaining suture has been deployed, a force
exerted in another direction (often substantially opposite to the
deployment direction) causes the retainers to be displaced from the
deployment position (i.e. resting substantially along the suture
body), forces the retainer ends to open (or "fan out") from the
suture body in a manner that catches and penetrates into the
surrounding tissue, and results in tissue being caught between the
retainer and the suture body; thereby "anchoring" or affixing the
self-retaining suture in place. In certain other embodiments, the
tissue retainers may be configured to permit motion of the suture
in one direction and resist movement of the suture in another
direction without fanning out or deploying. In certain other
configurations, the tissue retainer may be configured or combined
with other tissue retainers to resist motion of the suture filament
in both directions. Typically a suture having such retainers is
deployed through a device such as a cannula which prevents contact
between the retainers and the tissue until the suture is in the
desired location.
[0037] "Retainer configurations" refers to configurations of tissue
retainers and can include features such as size, shape,
flexibility, surface characteristics, and so forth. These are
sometimes also referred to as "barb configurations".
[0038] "Bidirectional suture" refers to a self-retaining suture
having retainers oriented in one direction at one end and retainers
oriented in the other direction at the other end. A bidirectional
suture is typically armed with a needle at each end of the suture
thread. Many bidirectional sutures have a transition segment
located between the two barb orientations.
[0039] "Transition segment" refers to a retainer-free (barb-free)
portion of a bidirectional suture located between a first set of
retainers (barbs) oriented in one direction and a second set of
retainers (barbs) oriented in another direction. The transition
segment can be at about the midpoint of the self-retaining suture,
or closer to one end of the self-retaining suture to form an
asymmetrical self-retaining suture system.
[0040] "Suture thread" refers to the filamentary body component of
the suture. The suture thread may be a monofilament, or comprise
multiple filaments as in a braided suture. The suture thread may be
made of any suitable biocompatible material, and may be further
treated with any suitable biocompatible material, whether to
enhance the sutures' strength, resilience, longevity, or other
qualities, or to equip the sutures to fulfill additional functions
besides joining tissues together, repositioning tissues, or
attaching foreign elements to tissues.
[0041] "Monofilament suture" refers to a suture comprising a
monofilamentary suture thread.
[0042] "Braided suture" refers to a suture comprising a
multifilamentary suture thread. The filaments in such suture
threads are typically braided, twisted, or woven together.
[0043] "Degradable suture" (also referred to as "biodegradable
suture" or "absorbable suture") refers to a suture which, after
introduction into a tissue is broken down and absorbed by the body.
Typically, the degradation process is at least partially mediated
by, or performed in, a biological system. "Degradation" refers to a
chain scission process by which a polymer chain is cleaved into
oligomers and monomers. Chain scission may occur through various
mechanisms, including, for example, by chemical reaction (e.g.,
hydrolysis, oxidation/reduction, enzymatic mechanisms or a
combination of these) or by a thermal or photolytic process.
Polymer degradation may be characterized, for example, using gel
permeation chromatography (GPC), which monitors the polymer
molecular mass changes during erosion and breakdown. Degradable
suture material may include polymers such as polyglycolic acid,
copolymers of glycolide and lactide, copolymers of trimethylene
carbonate and glycolide with diethylene glycol (e.g., MAXON.TM.,
Covidien), terpolymer composed of glycolide, trimethylene
carbonate, and dioxanone (e.g., BIOSYN.TM. [glycolide (60%),
trimethylene carbonate (26%), and dioxanone (14%)], Covidien),
copolymers of glycolide, caprolactone, trimethylene carbonate, and
lactide (e.g., CAPROSYN.TM. Covidien). A dissolvable suture can
also include partially deacetylated polyvinyl alcohol. Polymers
suitable for use in degradable sutures can be linear polymers,
branched polymers or multi-axial polymers. Examples of multi-axial
polymers used in sutures are described in U.S. Patent Application
Publication Nos. 2002/0161168, 2004/0024169, and 2004/0116620.
Sutures made from degradable suture material lose tensile strength
as the material degrades. Degradable sutures can be in either a
braided multifilament form or a monofilament form.
[0044] "Non-degradable suture" (also referred to as "non-absorbable
suture") refers to a suture comprising material that is not
degraded by chain scission such as chemical reaction processes
(e.g., hydrolysis, oxidation/reduction, enzymatic mechanisms or a
combination of these) or by a thermal or photolytic process.
Non-degradable suture material includes polyamide (also known as
nylon, such as nylon 6 and nylon 6,6), polyester (e.g.,
polyethylene terephthlate), polytetrafluoroethylene (e.g., expanded
polytetrafluoroethylene), polyether-ester such as polybutester
(block copolymer of butylene terephthalate and polytetra methylene
ether glycol), polyurethane, metal alloys, metal (e.g., stainless
steel wire), polypropylene, polyethelene, silk, and cotton. Sutures
made of non-degradable suture material are suitable for
applications in which the suture is meant to remain permanently or
is meant to be physically removed from the body.
[0045] "Suture diameter" refers to the diameter of the body of the
suture. It is to be understood that a variety of suture lengths may
be used with the sutures described herein and that while the term
"diameter" is often associated with a circular periphery, it is to
be understood herein to indicate a cross-sectional dimension
associated with a periphery of any shape. Suture sizing is based
upon diameter. United States Pharmacopeia ("USP") designation of
suture size runs from 0 to 7 in the larger range and 1-0 to 11-0 in
the smaller range; in the smaller range, the higher the value
preceding the hyphenated zero, the smaller the suture diameter. The
actual diameter of a suture will depend on the suture material, so
that, by way of example, a suture of size 5-0 and made of collagen
will have a diameter of 0.15 mm, while sutures having the same USP
size designation but made of a synthetic absorbable material or a
non-absorbable material will each have a diameter of 0.1 mm. The
selection of suture size for a particular purpose depends upon
factors such as the nature of the tissue to be sutured and the
importance of cosmetic concerns; while smaller sutures may be more
easily manipulated through tight surgical sites and are associated
with less scarring, the tensile strength of a suture manufactured
from a given material tends to decrease with decreasing size. It is
to be understood that the sutures and methods of manufacturing
sutures disclosed herein are suited to a variety of diameters,
including without limitation 7, 6, 5, 4, 3, 2, 1, 0, 1-0, 2-0, 3-0,
4-0, 5-0, 6-0, 7-0, 8-0, 9-0, 10-0 and 11-0.
[0046] "Needle attachment" refers to the attachment of a needle to
a suture requiring same for deployment into tissue, and can include
methods such as crimping, swaging, using adhesives, and so forth.
The suture thread is attached to the suture needle using methods
such as crimping, swaging and adhesives. Attachment of sutures and
surgical needles is described in U.S. Pat. Nos. 3,981,307,
5,084,063, 5,102,418, 5,123,911, 5,500,991, 5,722,991, 6,012,216,
and 6,163,948, and U.S. Patent Application Publication No. US
2004/0088003). The point of attachment of the suture to the needle
is known as the swage.
[0047] "Suture needle" refers to needles used to deploy sutures
into tissue, which come in many different shapes, forms and
compositions. There are two main types of needles, traumatic
needles and atraumatic needles. Traumatic needles have channels or
drilled ends (that is, holes or eyes) and are supplied separate
from the suture thread and are threaded on site. Atraumatic needles
are eyeless and are attached to the suture at the factory by
swaging or other methods whereby the suture material is inserted
into a channel at the blunt end of the needle which is then
deformed to a final shape to hold the suture and needle together.
As such, atraumatic needles do not require extra time on site for
threading and the suture end at the needle attachment site is
generally smaller than the needle body. In the traumatic needle,
the thread comes out of the needle's hole on both sides and often
the suture rips the tissues to a certain extent as it passes
through. Most modern sutures are swaged atraumatic needles.
Atraumatic needles may be permanently swaged to the suture or may
be designed to come off the suture with a sharp straight tug. These
"pop-offs" are commonly used for interrupted sutures, where each
suture is only passed once and then tied. For barbed sutures that
are uninterrupted, these atraumatic needles are preferred.
[0048] Suture needles may also be classified according to the
geometry of the tip or point of the needle. For example, needles
may be (i) "tapered" whereby the needle body is round and tapers
smoothly to a point; (ii) "cutting" whereby the needle body is
triangular and has a sharpened cutting edge on the inside; (iii)
"reverse cutting" whereby the cutting edge is on the outside; (iv)
"trocar point" or "taper cut" whereby the needle body is round and
tapered, but ends in a small triangular cutting point; (v) "blunt"
points for sewing friable tissues; (vi) "side cutting" or "spatula
points" whereby the needle is flat on top and bottom with a cutting
edge along the front to one side (these are typically used for eye
surgery).
[0049] Suture needles may also be of several shapes including, (i)
straight, (ii) half curved or ski, (iii) 1/4 circle, (iv) 3/8
circle, (v) 1/2 circle, (vi) 5/8 circle, (v) and compound
curve.
[0050] Suturing needles are described, for example, in U.S. Pat.
Nos. 6,322,581 and 6,214,030; and 5,464,422; and 5,941,899;
5,425,746; 5,306,288 and 5,156,615; and 5,312,422; and 7,063,716.
Other suturing needles are described, for example, in U.S. Pat.
Nos. 6,129,741; 5,897,572; 5,676,675; and 5,693,072. The sutures
described herein may be deployed with a variety of needle types
(including without limitation curved, straight, long, short, micro,
and so forth), needle cutting surfaces (including without
limitation, cutting, tapered, and so forth), and needle attachment
techniques (including without limitation, drilled end, crimped, and
so forth). Moreover, the sutures described herein may themselves
include sufficiently rigid and sharp ends so as to dispense with
the requirement for deployment needles altogether.
[0051] "Needle diameter" refers to the diameter of a suture
deployment needle at the widest point of that needle. While the
term "diameter" is often associated with a circular periphery, it
is to be understood herein to indicate a cross-sectional dimension
associated with a periphery of any shape.
[0052] "Armed suture" refers to a suture having a suture needle on
at least one suture deployment end. "Suture deployment end" refers
to an end of the suture to be deployed into tissue; one or both
ends of the suture may be suture deployment ends. The suture
deployment end may be attached to a deployment device such as a
suture needle, or may be sufficiently sharp and rigid to penetrate
tissue on its own.
[0053] "Wound closure" refers to a surgical procedure for closing
of a wound. An injury, especially one in which the skin or another
external or internal surface is cut, torn, pierced, or otherwise
broken is known as a wound. A wound commonly occurs when the
integrity of any tissue is compromised (e.g., skin breaks or burns,
muscle tears, or bone fractures). A wound may be caused by an act,
such as a puncture, fall, or surgical procedure; by an infectious
disease; or by an underlying medical condition. Surgical wound
closure facilitates the biological event of healing by joining, or
closely approximating, the edges of those wounds where the tissue
has been torn, cut, or otherwise separated. Surgical wound closure
directly apposes or approximates the tissue layers, which serves to
minimize the volume new tissue formation required to bridge the gap
between the two edges of the wound. Closure can serve both
functional and aesthetic purposes. These purposes include
elimination of dead space by approximating the subcutaneous
tissues, minimization of scar formation by careful epidermal
alignment, and avoidance of a depressed scar by precise eversion of
skin edges.
[0054] `Tissue elevation procedure" refers to a surgical procedure
for repositioning tissue from a lower elevation to a higher
elevation (i.e. moving the tissue in a direction opposite to the
direction of gravity). The retaining ligaments of the face support
facial soft tissue in the normal anatomic position. However, with
age, gravitational effects and loss of tissue volume effect
downward migration of tissue, and fat descends into the plane
between the superficial and deep facial fascia, thus causing facial
tissue to sag. Face-lift procedures are designed to lift these
sagging tissues, and are one example of a more general class of
medical procedure known as a tissue elevation procedure. More
generally, a tissue elevation procedure reverses the appearance
change that results from effects of aging and gravity over time,
and other temporal effects that cause tissue to sag, such as
genetic effects. It should be noted that tissue can also be
repositioned without elevation; in some procedures tissues are
repositioned laterally (away from the midline), medially (towards
the midline) or inferiorly (lowered) in order to restore symmetry
(i.e. repositioned such that the left and right sides of the body
"match").
[0055] "Medical device" or "implant" refers to any object placed in
the body for the purpose of restoring physiological function,
reducing/alleviating symptoms associated with disease, and/or
repairing and/or replacing damaged or diseased organs and tissues.
While normally composed of biologically compatible synthetic
materials (e.g., medical-grade stainless steel, titanium and other
metals or polymers such as polyurethane, silicon, PLA, PLGA and
other materials) that are exogenous, some medical devices and
implants include materials derived from animals (e.g., "xenografts"
such as whole animal organs; animal tissues such as heart valves;
naturally occurring or chemically-modified molecules such as
collagen, hyaluronic acid, proteins, carbohydrates and others),
human donors (e.g., "allografts" such as whole organs; tissues such
as bone grafts, skin grafts and others), or from the patients
themselves (e.g., "autografts" such as saphenous vein grafts, skin
grafts, tendon/ligament/muscle transplants). Medical devices that
can be used in procedures in conjunction with the present invention
include, but are not restricted to, orthopedic implants (artificial
joints, ligaments and tendons; screws, plates, and other
implantable hardware), dental implants, intravascular implants
(arterial and venous vascular bypass grafts, hemodialysis access
grafts; both autologous and synthetic), skin grafts (autologous,
synthetic), tubes, drains, implantable tissue bulking agents,
pumps, shunts, sealants, surgical meshes (e.g., hernia repair
meshes, tissue scaffolds), fistula treatments, spinal implants
(e.g., artificial intervertebral discs, spinal fusion devices,
etc.) and the like.
Laser-Cut Self-Retaining Sutures
[0056] As discussed above, the present invention provides laser
cutting apparatus and methods for cutting retainers on suture
thread. FIG. 1A illustrates a laser-cut self-retaining suture
system 100. Self-retaining suture system 100 comprises needles 110,
112 attached to self-retaining suture thread 102. Self-retaining
suture thread 102 includes a plurality of retainers 130 distributed
on the surface of a filament 120. In lead-in section 140 of
filament 120 there are no retainers 130. In section 142 of filament
120 there are a plurality of retainers 130 arranged such that the
suture can be deployed in the direction of needle 110, but resists
movement in the direction of needle 112. In transition section 144,
there are no retainers 130. In section 146, there is a plurality of
retainers 130 arranged such that the suture can be deployed in the
direction of needle 112, but resists movement in the direction of
needle 110. In lead-in section 148 of filament 120 there are no
retainers 130. A break is shown in each of sections 140, 142, 144,
146 and 148 to indicate that the length of each section may be
varied and selected depending upon the application for which the
suture is intended to be used. For example, transition section 144
can be asymmetrically located closer to needle 110 or needle 112,
if desired.
[0057] Self-retaining suture system 100 is composed of two arms.
Each arm may be considered to be a section of self-retaining suture
system 100. The first arm includes sections 142 and section 140 of
self-retaining suture thread 102 and a curved needle 110 has
relatively small retainer suitable for engaging harder/denser
tissue. The second arm includes sections 146 and 148 and needle 112
of self-retaining suture thread 102.
[0058] Although self-retaining suture system 100 of FIG. 1A has two
arms, in alternative embodiments, a self-retaining suture system
has single-armed sutures; dual-armed sutures; triple-armed sutures;
multiple-armed sutures; heterofunctional sutures having two or more
sections of suture having different features; dual-arm sutures
having different types (or sizes) of needles on each end; single or
dual-armed sutures for use with different layers/depth and types of
tissue; single or dual armed sutures with sections of filament
having different diameters for use with different layers/depth and
types of tissue.
[0059] Retainers 130 are laser-cut retainers formed on the surface
of filament 120 by cutting and/or ablating portions of the filament
with a laser as described below. The retainers 130 are in some
embodiments identical to one another. In alternative embodiments,
retainers 130, vary in shape, dimensions and/ or distribution in
different sections and/or within sections of the self-retaining
suture thread 102 as best suited for engaging tissue. It is an
advantage of self-retaining suture system having laser-cut
retainers that it is feasible to create multiple configurations of
retainers on a suture thread with a single cutting device as will
be described below.
[0060] FIG. 1B illustrates a magnified view of self-retaining
suture thread 102 in section 142. As shown in FIG. 1B, a plurality
of retainers 130 is distributed on the surface of filament 120. The
affixation of self-retaining sutures after deployment in tissue
entails the penetration of retainer ends 132 into the surrounding
tissue resulting in tissue being caught between the retainer 130
and the body of suture filament 120. The inner surface 134 of the
retainer 130 that is in contact with the tissue that is caught
between the retainer 130 and the body of filament 120, is referred
to herein as the "tissue engagement surface" or "inner retainer
surface." As illustrated in FIG. 1B, each retainer 130 has a tip
132 and tissue retainer surface 134. When self-retaining suture
thread 102 is moved in the direction of arrow 136, retainers 130
lies flat against the body of filament 120. However, when
self-retaining suture thread 102 is moved in the direction of arrow
138, tip 132 of retainer 130 engages tissue surrounding filament
120 and causes retainer 130 to fan out from filament 120 and engage
the tissue with tissue engagement surface 134 thereby preventing
movement of the suture in that direction.
[0061] FIG. 1C illustrates a magnified view of self-retaining
suture thread 102 in section 144. As shown in FIG. 1C, in section
144, there are no retainers 130. Section 144 may be referred to as
the transition section of self-retaining suture system 100. Section
144 may be deployed in either both of the directions shown by
arrows 136 and 138. In many procedures it is desirable to locate
the transition region in order to properly situate the transition
region at the beginning of suture deployment. Thus, the filament
120 in section 144 is, in some embodiments, provided with an
identifiable feature. For example, as shown in FIGS. 1A and 1C,
section 144 of self-retaining suture system 100 is provided with an
identifiable marker in the form of visible band 150. Band 150
represents a portion of filament 120 having a different visible
characteristic than other portions of filament 120 which can thus
be identified by a surgeon in order to identify and locate the
transition section 144 of self-retaining suture system 100. In
alternative embodiments, markers are provided on other sections of
the filament and/or needles in order to identify features of the
self-retaining suture system associated with the section marked.
Additionally, marker differences can include different shapes,
different colors, different numbers, and different letters to name
a few types of markers.
[0062] FIG. 1D illustrates a magnified view of self-retaining
suture thread 102 in section 146. As shown in FIG. 1D, a plurality
of retainers 130 is distributed on the surface of filament 120. As
illustrated in FIG. 1D, each retainer 130 has a tip 132 and tissue
retainer surface 134. When self-retaining suture thread 102 is
moved in the direction of arrow 138, retainer 130 lies flat against
the body of filament 120. However, when self-retaining suture
thread 102 is moved in the direction of arrow 136, tip 132 or
retainer 130 engages tissue surrounding filament 120 and causes
retainer 130 to fan out from filament 120 and engage the tissue
with face 134, thereby preventing movement of the suture in that
direction. Thus, in section 146 retainers 130 are oriented in the
opposite direction to the retainers 130 in section 142.
[0063] FIG. 1E illustrates an alternative embodiment of a
self-retaining suture system 160. Self-retaining suture system 160
includes needle 110 and sections 140, 142 and 144 of self-retaining
suture system 100 of FIG. 1A. However, self-retaining suture system
160 is a single-armed system. As shown in FIG. 1E, filament 120
terminates following section 146 in a tissue anchor 114e. Tissue
anchor 114e is a device for engaging tissue and preventing filament
120 from moving through tissue in the direction of needle 110.
Tissue anchor 114e is in some embodiments formed in one piece with
filament 120 or formed separately and subsequently attached to
filament 120. As shown in FIG. 1E, tissue anchor 114e has a
bar-shaped body 170e which extends approximately perpendicular to
the axis of filament 120. Bar-shaped body 170e is sufficiently long
and stiff to preclude movement of filament 120 in the direction of
needle 110 after tissue anchor 114e has engaged a tissue.
[0064] FIG. 1F shows an alternative anchor 114f which could be used
in place of tissue anchor 114e of FIG. 1E. As shown in FIG. 1F,
tissue anchor 114f comprises a conical body 170f. Conical body 170f
has a pointed end 172f and tissue engaging features 174f which
consist of ribs and/or barbs. Tissue anchor 114f is configured to
be pushed into tissue in order to anchor filament 120 to that
tissue and preclude movement of filament 120 in the direction of
needle 110.
[0065] FIG. 1G shows an alternative anchor 114g which could be used
in place of tissue anchor 114e of FIG. 1E. As shown in FIG. 1G,
tissue anchor 114g comprises a loop 170g. Loop 170g is, in this
embodiment, formed by folding back the end 172g of filament 120 and
securing end 172g to filament 120 by welding, fusing and/or
adhesive. Loop 170g is thus formed from the material of filament
120. Loop 170g has an aperture 174g through which needle 110 can
pass in order to create a noose which can be used to engage tissue
and preclude movement of filament 120 in the direction of needle
110.
[0066] FIG. 1H shows an alternative anchor 114h which could be used
in place of tissue anchor 114e of FIG. 1E. As shown in FIG. 1H,
tissue anchor 114h comprises a staple-shaped body 170h. Filament
120 passes through an aperture in anchor 114h and is secured by a
crimp 174h. Staple-shaped body 170h has two points pointed end 172h
which can be deformed towards each other to engage tissue and
preclude movement of filament 120 in the direction of needle
110.
Laser-Machining System for Creating Self-Retaining Sutures
[0067] In embodiments of the present invention, a laser machining
system is provided and utilized to create retainers on the surface
of a suture thread and/or provide visible markings on the suture
thread. The laser machining system uses a focused beam of coherent
light to selectively cut and/or ablate material from a suture
thread to generate retainers having a desired configuration on the
suture thread. The cutting/ablating process is a noncontact
process. A suitable laser machining system has very high spatial
confinement and control and very low heat deposition to the suture
thread so as to prevent damage to the suture thread during retainer
formation.
[0068] In general, a laser machining system is used to apply a
laser beam to a volume of material within a suture thread. The
laser energy is absorbed by the material which is thereby vaporized
and removed. The suture thread is, in some embodiments, provided
with a component which promotes absorption of the laser energy. The
laser light is provided at power, wavelength, and pulse duration
selected to vaporize the selected volume of suture material without
damaging the remaining suture thread. The wavelength of the laser
is typically in the range of UV to visible to infrared light. Light
as used herein is not limited to the visible spectrum. The ideal
wavelength or spectrum of wavelengths is selected to achieve the
best cutting/ablation characteristics.
[0069] The exposure required to cause the ablation/cutting may be
accomplished in one continuous exposure or a plurality of pulses.
Exposure to a plurality of laser pulses allows the energy of each
laser pulse to dissipate and therefore induces a lower temperature
rise in the suture thread than one continuous pulse of the same
total length. The power of the laser beam and/or pulse duration are
controlled to cut/ablate the desired material while delivering
insufficient total energy to the surrounding material to adversely
affect the bulk material properties of the suture thread. For
example, in a preferred embodiment a femtosecond laser is used
which provides high power for very short duration laser pulses. The
wavelength, power, focus and/or pulse duration are also controlled
to achieve the desired penetration of the laser into the suture
thread.
[0070] A variety of different lasers and control system can be used
to direct the laser to the selected locations of a suture to create
the retainers. In some embodiments, a steered beam system is used
to achieve the desired cutting/ablation. In a steered beam system a
pulsed laser is directed at a moving point on the suture thread.
Mirrors mounted on computer-controlled galvanometers are used to
direct the laser beam at targeted volumes of the suture thread. In
alternative embodiments, a mask or other optics are used to
generate a shaped laser beam having a suitable shape for achieving
the desired cutting/ablation. In alternative embodiments, a
stepwise pattern is used to create the laser marked indicia. A
volume of the suture material is targeted and ablated/cut by
modulating a laser on and off The suture and/or laser is then moved
to align a new target volume with the laser and the new target is
ablated/cut by modulating the laser on and off. The process is
continued to direct the beam stepwise or to move the suture thread
stepwise until the desired retainer configuration is achieved.
[0071] FIG. 2A is a schematic diagram of a laser-machining system
suitable for manufacturing self-retaining sutures. As shown in FIG.
2A, a laser-machining system 200 includes five subsystems. The five
subsystems of laser-machining system 200 are laser subsystem 210,
optics subsystem 220, imaging subsystem 230, transport subsystem
240 and control subsystem 250. Laser subsystem 210 supplies laser
power to laser machining system 200 in the form of laser beam 202.
Laser subsystem 210 is under control of control subsystem 250.
Laser subsystem 210 includes laser 212, laser attenuator 214 and
laser homogenizer 216. Laser 212 generates laser beam 202. Laser
attenuator 214 modulates laser beam 202, allowing it to pass and
blocking it as necessary under control of control subsystem 250.
Laser homogenizer 216 modifies the laser beam 202 to produce an
even power density across laser beam 202.
[0072] In a preferred embodiment, laser subsystem 210 is a
femtosecond laser system. A femtosecond laser system provides ultra
short pulses of laser energy suitable for cutting/ablating material
from a suture thread with a high degree of accuracy and without
causing damage to the surrounding suture thread. By using
femtosecond laser pulses, the laser energy is deposited into small
volumes of material by optical absorption followed by avalanche
ionization of the material. The laser energy is deposited at a time
scale much shorter than the timescale for heat transport in the
material. Thus, the material targeted by the laser beam is
transformed from solid to vapor phase and to plasma formation
almost instantaneously and without significant heat transfer to the
surrounding material. The femtosecond laser pulses thus reduce
thermal damage to the suture thread.
[0073] A femtosecond laser is advantageous because it can achieve:
high resolution and repeatability in a fully automated system; high
aspect ratios for cutting/ablation of suture thread with low
redeposition of ablated material; very localized effects and little
damage to suture thread adjacent cutting/ablation zone; and
effective cutting of suture thread material over a wide range of
materials and diameters (including, for example USP 12-0 to 7). For
example, a femtosecond laser system can cut/ablate suture material
with submicron resolution and nanometer scale surface roughness of
cut surfaces. The parameters of the femtosecond laser can be
adjusted to achieve the desired resolution, aspect ratio and reduce
collateral damage including by selecting: the appropriate
wavelength or combination of wavelengths; the power distribution of
the beam (Gaussian, Top hat, axiconic to provide an annular ring
profile); the beam energy and pulse duration; and the focal length
and depth of focus for the optics system. The parameters are in
some cases modified for different suture thread materials and
diameters and retainer configurations.
[0074] Laser beam 202 passes from laser subsystem 210 to optics
subsystem 220. Optics subsystem 220 includes one or more mirrors
222 and lenses for directing and/or focusing laser beam 202 at a
desired target. In particular, optics subsystem 220 includes an
object lens 224 from which laser beam 202 leaves optic subsystem
220 towards the desired target. Optics subsystem 220 also includes
one or more actuators 226, 228 under control of computer subsystem
250 for adjusting the positions of the mirror(s) 222 and lens(es)
224.
[0075] Imaging subsystem 230 allows observation of suture thread
204 and monitoring of the results of laser machining upon it.
Imaging subsystem 230 includes an imaging device 232 which is in
some embodiments a camera. Imaging system also includes an
illumination device 234 for illuminating suture thread 120. Imaging
subsystem 230 can also include one or more mirrors and lenses for
directing light to and from suture thread 202. Imaging subsystem
230 provides images of suture thread 204 to control subsystem 250.
In a preferred embodiment, imaging subsystem 230 is provided
in-line with optics subsystem 220 as shown. That is to say that
illumination device 234 delivers illumination to suture thread 204
and imaging device 232 receives an image of suture thread 204
through the optic subsystem 220. The images of suture thread 204
can be used by control subsystem 250 to verify the correct
operation of the laser subsystem 210 and optics subsystem 220 and
make configuration adjustments as necessary. Advantageously image
data from the imaging subsystem 230 can be used by the control
subsystem 250 to monitor and adjust the depth of focus of the optic
system to allow proper focusing and targeting of the laser beam. In
alternative embodiments, an off-line imaging system can be used.
The images of the suture thread 204 can also be used for quality
control of retainer formation including, in some embodiments,
validating the correct creation of 100% of the retainers.
[0076] Transport subsystem 240 operates to support suture thread
204 and move suture thread 204 relative to laser beam 202. The
laser subsystem 210, imaging subsystem 230, optics subsystem 220
and transport subsystem 240 are all securely mounted to a bench 206
to prevent relative movement/vibration of the systems except as
controlled by transport subsystem 240. Transport subsystem 240
includes chucks 242 for holding each end of suture thread 204.
Chucks 242 are preferably driven by an actuator 243 which drives
rotation of suture thread 204 around the longitudinal axis of the
suture thread 204. Chucks 242 are mounted to an XY positioning
stages 244, 246. XY positioning stages 244, 246 are preferably
driven by actuators 245, 247 which control the position of the
suture thread 204 relative to the laser beam 202. XY positioning
stages 244, 246 are preferably aligned with the longitudinal axis
of suture thread 204 such that one stage controls movement of the
suture thread along its longitudinal axis relative to laser beam
202 and the other stage controls movement of suture thread 204
perpendicular to the longitudinal axis (across the laser beam 204).
Actuators 243, 245, 247 are preferably under the control of control
subsystem 250. Transport subsystem 240, in some embodiments,
includes a suture spool and mechanism (not shown) for automatically
feeding lengths of suture thread to be held between chucks 242
without the need for rethreading the suture thread.
[0077] Transport subsystem 240 also includes a stabilization device
248 for stabilizing suture thread 204 adjacent the laser beam 202.
Stabilization device 248 reduces movement of suture thread 204
adjacent the cutting region in order to enhance the accuracy of the
laser machining operation. In preferred embodiment stabilization
device 248 is an air bearing which provides a stream of air to
stabilize suture thread 204 without mechanically contacting suture
thread 204. The stream of air also serves to cool the suture thread
204 and eliminate smoke and particles from the cutting region.
[0078] Control subsystem 250 is a general purpose machine control
system having outputs for controlling actuators and inputs for
receiving data from machine sensors. Control subsystem 250 includes
memory for program and data storage. The program and data storage
includes parameters for operation of the laser subsystem 210,
optics subsystem 220, imaging subsystem 230, and transport
subsystem 240 and/or recorded diagnostic and performance data
concerning the operation of laser machining system 200. Data may be
stored in control subsystem 250 or other data storage associated
with the local network or WAN. Data may be stored in a single
format or in multiple formats. Data may be stored on a single type
of media or on multiple types of media e.g. hard disks, RAM, flash
memory, floppy disks, web-storage systems, etc.
[0079] Control subsystem 250 includes one or more processors 252
which can be a computer processer, CPU, and typically includes a
microcontroller, CPU, microprocessor or equivalent control
circuitry or processor, designed specifically for controlling the
laser machining system 200, and may further include RAM or ROM
memory, logic and timing circuitry, state machine circuitry, and
I/O circuitry. The control system contains and/or has access to
programs and/or data which define the distribution of retainers to
be formed on a filament and the shape/shapes of the retainers to be
formed on the filament as well as the tolerances for the expected
shape/shapes of the retainers. The details of the design of control
subsystem 250 are not critical to the present invention. Rather,
any suitable control subsystem 250 may be used that carries out the
functions described herein. The use of
computer/microprocessor-based control systems for controlling
machine tools is well known in the art.
[0080] In an embodiment, the laser beam provided by laser subsystem
210 and optic subsystem 220 has a Gaussian power density
distribution. FIG. 2B shows a representative image of a Gaussian
laser beam 260 incident on a planar surface 268. As shown in FIG.
2B, the power density of Gaussian beam 260 drops off rapidly moving
away from a peak at the center 262 of the beam 260. The diameter D
of the zone of peak power density can be altered using the optic
subsystem to focus the laser beam. FIG. 2C shows a graphical
representation of the power density distribution of Gaussian laser
beam (such as laser beam 260 of FIG. 2B).
[0081] An alternative laser beam shape/power distribution can be
achieved by the use of an axicon prism system utilizing two axicon
(rotationally revolved prism) and a lens. The first axicon produces
a ring, the lens focuses the ring to a thin (5 micron) width and
the second axicon collimates the ring. Varying the distance between
the axicon prisms provides the ability to control the diameter of
the ring from 0 microns to 300 microns while maintaining focus. The
axicon prism system can be used to machine cones into the suture
material at an angle. Cones of various diameters are used in a
laser machining process to remove material from a filament. By
adjusting the cone diameter and the angle of cone relative to the
retainer/filament a wide variety of retainer configuration can be
machined which would not be possible with a standard laser beam or
mechanical cutting. For example, the cone produced by the axicon
pair is in some embodiments set to be near 0 diameter,
progressively getting larger while the focus of the laser is
translated into the suture removing a 3D cone shape of suture
material (at a compound angle relative to a retainer to be formed).
The laser power is coordinated with the cone diameter to maintain a
constant energy density in the ring regardless of ring
diameter.
[0082] FIG. 2D shows a representative image of a laser beam 270
from an axicon prism system incident on a planar surface 278. As
shown in FIG. 2E the laser beam has a low power density at the
center 272. The power density increases travelling away from center
272 until it peaks in ring 274. The power density then drops off
rapidly moving outward from ring 274. The diameter D of ring 274
can be controlled by changing the distance between the axicon
prisms. The thickness T of the ring can be controlled using the
lens between the axicon prisms to focus the ring. FIG. 2E shows a
graphical representation of the power density distribution of a
laser beam (such as laser beam 270 of FIG. 2D) from an axicon prism
system, where the axicon prism essentially creates an energy
distribution having a profile in the form of an annular ring.
[0083] FIG. 3A shows a sectional view of an embodiment of a
stabilization device 248 for stabilizing suture thread 204 adjacent
the laser beam 202 (see FIG. 2A). The stabilization device 248
reduces movement of suture thread 204 adjacent the cutting region
in order to enhance the accuracy of the laser machining operation
(see FIG. 2A). As shown in FIG. 3A, a preferred embodiment of
stabilization device 248 is an air bearing 300 which provides a
stream of air to stabilize suture thread 304 without mechanically
contacting suture thread 304. FIG. 3A shows a sectional view of an
air bearing 300 which can be included in stabilization device 248
of FIG. 2A. As shown in FIG. 3A, air bearing comprises an entry
nozzle 310 and an exit nozzle 320. Entry nozzle 310 and exit nozzle
320 have tips 312, 322 which have an inside diameter as close as
possible to the diameter of the suture without running the risk of
making physical contact. The inside diameter may be 1.5, 2.0, 2.5
or 3.0 times the suture diameter, however as the inside diameter
increases, there is a greater tendency for looseness in the fluid
film bearing. Thus, it is preferred to have the inside diameter
under two times the suture diameter, and more preferably less than
1.5 times the suture diameter. In preferred embodiments, different
nozzles are used for suture threads of different size. Entry nozzle
310 and exit nozzle 320 can be made by drawing down a glass tube to
the appropriate diameter for a particular suture thread and cutting
and grinding the tip 312, 322. An alternative and suitable air
bearing is available from Newway Air Bearings (Aston, Pa.) which
incorporates graphite porous media for the bearing and utilizes the
air brushing approach in a size suitable for sutures.
[0084] As shown in FIG. 3A, exit nozzle 320 is mounted within a
cavity 332 of a manifold 330. O-rings 340, 342 seal exit nozzle 320
to the surface of cavity 332. Manifold 330 is machined to deliver
pressurized air from an intake line 334 evenly around cavity 332.
Entry nozzle 310 is positioned with tip 312 within the lumen of
exit nozzle 320 as shown. Entry nozzle 310 and exit nozzle 320 are
positioned coaxially. Entry nozzle 310 is aligned and secured in
position by entry cap 350. An o-ring 344 seals entry nozzle 310 to
entry cap 350. Entry cap 350 has a chamfered entry port 352 which
is positioned coaxial with entry nozzle 310 and exit nozzle 320. An
exit cap 354 is mounted on the other end of manifold 330. Exit cap
354 has an exit port 356 through which exit nozzle 320 protrudes.
Entry cap 350, manifold 330 and exit cap 354 are secured together
by a plurality of fasteners 358.
[0085] A suture thread 304 can be introduced through entry port
352. Suture thread 304 passes through entry nozzle 310 and then
through exit nozzle 320 passing out of tip 322 of exit nozzle 320
as shown. Pressurized air is introduced through intake 334 and
passes into the cavity 332 of manifold 330. The pressurized air the
passes into exit nozzle 320 and is forced out of tip 322
surrounding suture thread 304. (Some air also leaks out through
entry nozzle 310). The fast moving air surrounding suture thread
304 operates as an air bearing stabilizing the position of suture
thread 304 adjacent tip 322 without contacting suture thread
304.
[0086] FIG. 3B, shows a perspective view only of exit nozzle 320
and suture thread 304. As shown in FIG. 3B pressurized air enters
the lumen 324 of exit nozzle 320 (arrows 360 and is forced at high
speed out of the narrow tip 322 of exit nozzle (arrows 362). The
stream of air within tip 322 stabilizes suture thread within the
center of tip 322 and so suture thread does not contact the walls
of exit nozzle 320. Furthermore, a stream of high speed air
surrounds suture thread 304 as it exits tip 322. The tip is
designed to produce laminar flow of air in this stream in an area
adjacent the tip. In this laminar flow zone, the high speed stream
of air stabilizes the suture thread damping movement and vibration
caused e.g. by the cutting process. Pressure is exerted by slower
moving gas on the outside of the high speed stream forcing suture
thread 304 to the center of stream as shown by arrows 364. Thus,
the suture thread 304 is stabilized by the air bearing in the
region 370 adjacent tip 322 of exit nozzle 320. The air bearing 300
is positioned so that stabilization region 370 is positioned in the
cutting zone of the laser. The stream of air passing over suture
thread 304 also serves to remove particulates and smoke from the
laser cutting process and also cools the suture thread 304 during
cutting by the laser. The suture thread is passes out of the tip
332 of exit nozzle 320 for cutting of retainers in the
stabilization zone. After cutting the retainers are moved away from
exit nozzle 320. It is preferred that the retainers not move into
the exit nozzle as the high velocity air can damage the retainers,
and the retainers can cause turbulence in the high velocity air
destabilizing the suture thread in stabilization region 370.
[0087] For cutting USP 2-0 blue polypropylene suture material
without an air bearing (See FIGS. 3A-3B) the following femtosecond
laser parameters were found effective: a 10.times. objective 0.26
N.A. lens; 26 mW average laser power; 775 nm laser wavelength:
(frequency doubled and mode locked erbium fiber laser with Titanium
Sapphire chirped pulse amplifier; a pulse width 122 femtoseconds;
an RF Divider establishing a 3 kHz pulse rate; and a cutting speed
of 9.5 mm/minute. The best cutting results were achieved by
penetrating the suture within the body of the filament and then
moving outward to edge. For cutting USP 4-0 blue propylene suture
material the following femtosecond laser parameters were found
effective: a 20.times. objective lens, 36 mW average laser power;
and a cutting speed of 10 mm/minute. With these parameters each
retainer took only 1.16 second to create. Addition of an air
bearing allowed retainers to be created more effectively on USP
2-0, 4-0 and 6-0 blue polypropylene suture material because of e.g.
stabilization of the filament and cooling of the filament during
cutting. However, use of UV wavelengths was found to be more
effective for cutting the blue polypropylene suture material as it
vaporizes the suture material more effectively with less heating of
surrounding material. In a preferred embodiment a combination of UV
and IR wavelength is used to ablate material with about 70% or more
of the energy being supplied in the UV wavelength.
[0088] FIG. 4A is a flowchart of a method 400 for operating the
laser machining system 200 of FIG. 2A. In the first step 402, the
suture thread is mounted to the chucks of the transport system. The
suture thread should also be tensioned to a desired tension during
the mounting step. The tension should be the same for each suture
thread. At step 404, the control system operate the transport
subsystem is operated to index and rotate the suture thread to the
correct position for forming the first retainer. The
distribution/location of retainers is stored in a retainer
distribution pattern data or program file. At step 406, the control
subsystem selects the correct retainer creation pattern for the
indexed location on the suture thread. The retainer creation
pattern dictates the final orientation, shape and size of the
retainer to be created at a particular location.
[0089] The laser machining system is then operated to form a
retainer at the indexed location in accordance with the selected
retainer creation pattern. At step 408, the transport system is
operated to align a target volume of the suture thread with the
laser. At step 410, the laser subsystem is operated to ablate/cut
material in the target volume. Step 410 can also include validation
of the ablation/cutting using the imaging subsystem. At step 412,
if further material needs to be ablated/cut to form the retainer,
the process returns to step 408 to operate the transport system to
align a new target volume with the laser in accordance with the
retainer creation pattern. At step 412, if the laser creation
pattern is completed, the process moves on to step 414.
[0090] At step 414, the imaging subsystem is operated to image the
completed retainer and provide the image data to the control
subsystem. The control subsystem uses the image data to validate
that the retainer is within the tolerances defined by the retainer
creation pattern. If the retainer cannot be validated, the control
system can do one or more of: operate the transport subsystem and
laser subsystem to correct the defect; fail the particular suture
thread; mark an exception with respect to the suture thread for
further inspection; set an alert for a human operator; and/or shut
down operation of the laser-machining system. If the retainer is
validated within tolerances at step 414 the process moves on to
step 416. At step 416, if further retainers remain to be created,
the process return to step 404 for indexing the suture thread to
the next position for creating a retainer. At step 416, if all
retainers have been completed, the process moves to step 418. At
step 418 the suture thread is complete and is unloaded from the
chucks.
[0091] FIGS. 4B-4D further illustrate steps in the process of
forming a retainer according to the method of FIG. 4A. As shown in
FIG. 4B, the suture thread 424 is moved longitudinally 430,
laterally (432) and axially (434) by the transport subsystem to
align the laser beam 426 with a target volume of the suture thread
424. The laser subsystem is then operated to ablate material from
the suture thread 424, generating a cavity or slot 428. Note that
cavity 428 is larger in diameter than laser beam 426. In an
embodiment, a laser beam 3 nm in diameter generates a cavity of
approximately 7 nm in diameter.
[0092] As shown in FIG. 4C, the suture thread 424 is moved
longitudinally 430 and laterally 432 stepwise to a series of
positions aligning new target volumes with the laser beam to
generate a series of cavities through suture thread 424. The target
volumes are dictated by the suture creation pattern. Note that it
is preferable to make interior cuts to form the tissue engagement
surface of the retainer prior to cutting the tip of the
retainer.
[0093] FIG. 4D shows the completed retainer 440 having a tip 442
and retainer engagement surface 444. Note that tip 442 is not
elevated above the surface of suture thread 424. Post-cut
processing can be carried out in some cases to elevate the tip
above the surface of the suture thread 424. In other embodiments,
the retainer 440 is designed to be effective without elevation of
the retainer tip 442 above the original surface of the suture
thread 424. The same steps are repeated for the remaining retainers
on suture thread 424. Note that different configurations and
orientations of retainer can be created at different locations on
the suture using a different retainer creation pattern without
requiring a different cutting head or reloading the suture thread.
An advantage of utilizing a laser-machining system to create
retainers is the ability to form retainers in configurations that
are difficult and/or impossible to make using mechanical cutting
with a blade.
[0094] A retainer was cut on USP 2-0 blue polypropylene suture
thread. The retainer was removed and the laser-cut surface of a
self-retaining suture was examined for flatness and uniformity. The
laser-cut tissue engagement surface of the retainer (not shown)
should have similar characteristics of flatness and uniformity.
FIG. 5 shows an image of the examined laser cut surface 922
machined into a suture thread 920. FIG. 6 shows a graph of the
profile of laser-cut surface viewed laterally. The laser machining
system is shown to make laser-cut surfaces of high flatness and
uniformity with high precision and repeatability to create a
self-retaining suture.
[0095] FIG. 7 show a range of retainer distributions and patterns
that can be created using the laser machining system. FIG. 7 shows
a single helix distribution which may be cut with the laser
machining system of the present invention. The laser-cut retainers
can have any laser-cut retainer configuration described herein
and/or different laser-cut retainer configurations can be present
at different points of the self-retaining suture. Note also that
the laser machining system of the present invention is capable of
creating non-uniform retainer distributions along a single suture
thread if advantageous for a particular self-retaining suture
application.
[0096] Referring first to FIG. 7 which shows a single helix
distribution of laser-cut retainers 704 on a self-retaining suture
700. As shown in FIG. 7, the self-retaining suture 700 has a
filament 702 which is of USP 2-0, 4-0, 6-0, 7-0, 8-0, 9-0, 10-0,
11-0, 12-0 or below. As shown in FIG. 7, the filament is 0.25 mm in
diameter which is a 4-0 suture. The self-retaining suture 700
includes a plurality of laser-cut retainers 704 arranged in a
helical pattern around and along the filament 702. As shown in FIG.
7, the helix has a pitch of 4.46 mm (or 5.7 twists per inch). The
distance between the base of one laser-cut retainer and the base of
the adjacent laser-cut retainer in the same helix is 0.6
mm--measured axially--see arrow 718. In an embodiment, the
self-retaining suture has a barbed section 712 at least 70 mm in
length and a 100 mm unbarbed lead 710, 714 on either side of the
barbed section 712. The barbed section 712 may have retainers 704
in one orientation or in different orientations. Note that because
the laser machining system is contactless, retainer distribution
patterns can be designed without limitations imposed by the need to
support a suture without impairing already cut retainers during
mechanical cutting. Thus, for example, in some embodiments, the
pitch can be less than the length of a retainer.
[0097] Note that because the laser machining system is contactless,
retainer distribution patterns can be designed without limitations
imposed by the need to support a suture without impairing already
cut retainers during mechanical cutting. Thus, for example, in some
embodiments the pitch can be less than the length of a
retainer.
Examples of Self-Retaining Sutures with Laser-Cut Retainers
[0098] FIGS. 8A-8B are images of examples of laser-cut retainers
created with the laser cutting system of FIG. 2A. Self-retaining
sutures comprising suture threads with a plurality of laser-cut
retainers thereon made to test the capabilities of a
laser-machining system in accordance with FIG. 2A. The suture
threads were, in each case blue-colored propylene filaments.
[0099] FIG. 8A shows an image of 2-0 polypropylene suture 820
having laser-cut retainers 822 thereon. Laser-cut retainers 822
have a straight cut configuration and are distributed in a
double-helix distribution. After the retainers 822 were cut, the
suture 820 was heat treated for five minutes at 155 C while under
32 grams of tension to elevate the retainers 822.
[0100] FIG. 8B shows an image of 10-0 polypropylene suture 800
having laser-cut retainers 802 thereon. Laser-cut retainers 802
have a straight cut configuration.
[0101] FIG. 8C shows an image of a polypropylene suture 860 having
laser-cut retainers 862 thereon. Laser-cut retainers 862 have a
straight cut configuration and are distributed in a double-helix
distribution. After the retainers 862 were cut, the suture 860 was
heat treated for five minutes at 155 C to elevate the retainers
862. The resulting parameters L1-L5 of suture 860 were then
measured under a microscope. The suture diameter L1 was 101.8 nm;
the cut length L2 was 99.5 nm; the cut depth L3 was 34.5 nm; the
elevation L4 of the tip of the retainer above the surface of the
filament was 15.8 nm; and the distance L5 between adjacent
retainers was 118.3 nm.
[0102] FIG. 8D shows an image of a polypropylene suture 870 having
laser-cut retainers 872 thereon. Laser-cut retainers 872 have a
straight cut configuration and are distributed in a double-helix
distribution. After the retainers 872 were cut, the suture 870 was
heat treated for five minutes at 155 C to elevate the retainers
872. The resulting parameters L1-L4 and AN1 of suture 870 were then
measured under a microscope. The suture diameter L3 was 103.8 nm;
the cut depth L2 was 29.7 nm; the elevation L1 of the tip of the
retainer above the surface of the filament was 14.6 nm; the
distance L4 between adjacent retainers was 131.3 nm; and the angle
AN1 was 14.3 degrees.
[0103] FIG. 8E shows an image of a polypropylene suture 880 having
laser-cut retainers 882 thereon. Laser-cut retainers 882 have a
straight cut configuration and are distributed in a double-helix
distribution. After the retainers 882 were cut, the suture 880 was
heat treated for five minutes at 155 C to elevate the retainers
882. The resulting parameters L1-L6 of suture 880 were then
measured under a microscope. The suture diameter L6 was 93.3 nm;
the width L1 of the retainer base was 77.6 nm; the cut length L3
was 69.2 nm; the cut depth L4 was 28.5 nm; the elevation L5 of the
tip of the retainer above the surface of the filament was 14.6 nm;
and the distance L2 between adjacent retainers was 89.1 nm.
[0104] FIG. 8F shows an image of a polypropylene suture 890 having
laser-cut retainers 892 thereon. Laser-cut retainers 892 have a
straight cut configuration and are distributed in a double-helix
distribution. After the retainers 892 were cut, the suture 890 was
heat treated for five minutes at 155 C to elevate the retainers
892. The resulting parameters L1-L6 and AN1 of suture 890 were then
measured under a microscope. The suture diameter L5 was 96.5 nm;
the width L6 of the retainer base was 83.4 nm; the cut length L1
was 107.9 nm; the cut depth L2 was 37.0 nm; the elevation L3 of the
tip of the retainer above the surface of the filament was 21.2 nm;
the distance L4 between adjacent retainers was 117.2 nm; and angle
An1 was 18 degrees.
Materials
[0105] Suture threads described herein may be produced by any
suitable method, including without limitation, injection molding,
stamping, cutting, laser, extrusion, and so forth. The suture
threads described herein may use any material conventionally used
for the manufacture of sutures including for example, metals and
metal alloys, polymers including non-degradable polymers and
biodegradable polymers, and natural materials. With respect to
cutting, polymeric suture threads/filaments may be manufactured or
purchased for the suture body, and the retainers can be
subsequently cut onto the suture body. During cutting, either the
laser beam or the suture thread may be moved relative to the other,
or both may be moved, to control the size, shape and depth of the
retainers.
[0106] It is an advantage of the laser-machining system described
herein that it is operative to form retainers on a wide range of
suture materials. Suitable suture materials include: degradable
suture materials, non-degradable suture materials, natural suture
materials, recombinant suture materials and metallic suture
materials. Degradable suture materials (also referred to as
"biodegradable suture" or "absorbable suture") are those which,
after introduction into a tissue are broken down and absorbed by
the body. Typically, the degradation process is at least partially
mediated by, or performed in, a biological system. "Degradation"
refers to a chain scission process by which a polymer chain is
cleaved into oligomers and monomers. Chain scission may occur
through various mechanisms, including, for example, by chemical
reaction (e.g., hydrolysis, oxidation/reduction, enzymatic
mechanisms or a combination of these) or by a thermal or photolytic
process. Polymer degradation is, in some embodiments,
characterized, for example, using gel permeation chromatography
(GPC), which monitors the polymer molecular mass changes during
erosion and breakdown. Non-degradable suture materials (also
referred to as "non-absorbable suture") are those which are not
degraded by chain scission such as chemical reaction processes
(e.g., hydrolysis, oxidation/reduction, enzymatic mechanisms or a
combination of these) or by a thermal or photolytic process.
[0107] Degradable suture materials include polymers for example
polyglycolic acid, copolymers of glycolide and lactide, copolymers
of trimethylene carbonate and glycolide with diethylene glycol
(e.g., MAXON.TM., Tyco Healthcare Group), terpolymer composed of
glycolide, trimethylene carbonate, and dioxanone (e.g., BIOSYN.TM.
[glycolide (60%), trimethylene carbonate (26%), and dioxanone
(14%)], Tyco Healthcare Group), copolymers of glycolide,
caprolactone, trimethylene carbonate, and lactide (e.g.,
CAPROSYN.TM., Tyco Healthcare Group). A dissolvable suture can also
include partially deacetylated polyvinyl alcohol. Polymers suitable
for use in degradable sutures can be linear polymers, branched
polymers or multi-axial polymers. Examples of multi-axial polymers
used in sutures are described in U.S. Patent Application
Publication Nos. 2002/0161168, 2004/0024169, and 2004/0116620.
Sutures made from degradable suture material lose tensile strength
as the material degrades. Degradable sutures can be in either a
braided multifilament form or a monofilament form.
[0108] Non-degradable suture materials include, for example,
polyamide (also known as nylon, such as nylon 6 and nylon 6,6),
polyester (e.g., polyethylene terephthlate),
polytetrafluoroethylene (e.g., expanded polytetrafluoroethylene),
polyether-ester such as polybutester (block copolymer of butylene
terephthalate and polytetra methylene ether glycol), polyurethane,
metal alloys, metal (e.g., stainless steel wire), polypropylene,
polyethelene, silk, and cotton. Sutures made of non-degradable
suture material are suitable for applications in which the suture
is meant to remain permanently in the body or is meant to be
physically removed from the body after it has served its intended
purpose.
Clinical Uses
[0109] In addition to the general wound closure and soft tissue
repair applications, self-retaining sutures can be used in a
variety of other indications.
[0110] Self-retaining sutures described herein may be used in
various dental procedures, i.e., oral and maxillofacial surgical
procedures and thus may be referred to as "self-retaining dental
sutures." The above-mentioned procedures include, but are not
limited to, oral surgery (e.g., removal of impacted or broken
teeth), surgery to provide bone augmentation, surgery to repair
dentofacial deformities, repair following trauma (e.g., facial bone
fractures and injuries), surgical treatment of odontogenic and
non-odontogenic tumors, reconstructive surgeries, repair of cleft
lip or cleft palate, congenital craniofacial deformities, and
esthetic facial surgery. Self-retaining dental sutures may be
degradable or non-degradable, and may typically range in size from
USP 2-0 to USP 6-0.
[0111] Self-retaining sutures described herein may also be used in
tissue repositioning surgical procedures and thus may be referred
to as "self-retaining tissue repositioning sutures". Such surgical
procedures include, without limitation, face lifts, neck lifts,
brow lifts, thigh lifts, and breast lifts. Self-retaining sutures
used in tissue repositioning procedures may vary depending on the
tissue being repositioned; for example, sutures with larger and
further spaced-apart retainers may be suitably employed with
relatively soft tissues such as fatty tissues.
[0112] Self-retaining sutures described herein may also be used in
microsurgical procedures that are performed under a surgical
microscope (and thus may be referred to as "self-retaining
microsutures"). Such surgical procedures include, but are not
limited to, reattachment and repair of peripheral nerves, spinal
microsurgery, microsurgery of the hand, various plastic
microsurgical procedures (e.g., facial reconstruction),
microsurgery of the male or female reproductive systems, and
various types of reconstructive microsurgery. Microsurgical
reconstruction is used for complex reconstructive surgery problems
when other options such as primary closure, healing by secondary
intention, skin grafting, local flap transfer, and distant flap
transfer are not adequate. Self-retaining microsutures have a very
small caliber, often as small as USP 9-0, USP 10-0, USP 11-0 or USP
12-0, and may have an attached needle of corresponding size. The
microsutures may be degradable or non-degradable.
[0113] Self-retaining sutures as described herein may be used in
similarly small caliber ranges for ophthalmic surgical procedures
and thus may be referred to as "ophthalmic self-retaining sutures".
Such procedures include but are not limited to keratoplasty,
cataract, and vitreous retinal microsurgical procedures. Ophthalmic
self-retaining sutures may be degradable or non-degradable, and
have an attached needle of correspondingly-small caliber. In
addition, the self-retaining sutures disclosed herein can be used
in a variety of veterinary applications for a wide number of
surgical and traumatic purposes in animal health.
[0114] Thus, as described more fully herein, the present invention
includes, in some embodiments, laser cutting systems, components
and methods as identified in the following numbered paragraphs:
[0115] A method for making a self-retaining suture comprising;
[0116] (a) identifying a tissue retainer location on the suture
thread; [0117] (b) directing a laser beam at the tissue retainer
location on the suture thread; [0118] (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; [0119] (d) repeating steps (a), (b) and (c) to
generate a plurality of tissue retainers on the suture thread.
[0120] The method of paragraph 115, wherein step (c) comprises
[0121] (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 [0122] (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.
[0123] The method of paragraph 115, 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 .mu.m.
[0124] The method of paragraph 115, wherein step (b) comprises
directing a femtosecond laser beam at the tissue retainer location
on the suture thread.
[0125] The method of paragraph 115, wherein step (b) comprises
directing a femtosecond laser beam comprising infrared wavelengths
at the tissue retainer location on the suture thread.
[0126] The method of paragraph 115, wherein step (b) comprises
directing a femtosecond laser beam comprising ultraviolet
wavelengths at the tissue retainer location on the suture
thread.
[0127] The method of paragraph 115, further comprising: [0128] (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.
[0129] The method of paragraph 115, further comprising: [0130] (e)
after completion of step (d) heating the suture thread to cause a
tip of each of said plurality of retainers to elevate above a
surface of said suture thread.
[0131] The method of paragraph 115, further comprising: [0132] (e)
after completion of step (d) applying tension to the suture thread
to cause a tip of each of said plurality of retainers to elevate
above a surface of said suture thread.
[0133] The method of paragraph 115, further comprising: [0134] (e)
after completion of step (d) applying heat and tension to the
suture thread to cause a tip of each of said plurality of retainers
to elevate above a surface of said suture thread.
[0135] The method of paragraph 115, further comprising: [0136] (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 [0137] (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.
[0138] A laser-machining system adapted to make tissue retainers on
a suture thread, wherein the laser-machining system comprises:
[0139] a laser subsystem adapted to provide a laser beam;
[0140] an optic system adapted to receive the laser beam and
generate a focused laser beam directed at a volume of the suture
thread;
[0141] a transport subsystem adapted to move the suture thread
relative to the laser beam;
[0142] an imaging subsystem adapted to image the suture thread and
generate image data; and
[0143] 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.
[0144] The laser-machining system of paragraph 126, wherein:
[0145] the laser subsystem comprises a femtosecond laser.
[0146] The laser-machining system of paragraph 126, wherein:
[0147] the laser subsystem comprises a UV laser.
[0148] The laser-machining system of paragraph 126, wherein:
[0149] the laser subsystem comprises an IR laser.
[0150] The laser-machining system of paragraph 126, wherein:
[0151] the laser subsystem is adapted to provide a laser beam
including IR and UV wavelengths.
[0152] The laser-machining system of paragraph 126, wherein:
[0153] the control subsystem provides focus control signals to the
optical subsystem in response to the image data; and
[0154] the optic subsystem is adapted to change the focus depth of
the laser beam in response to the focus control signals.
[0155] The laser-machining system of paragraph 126, wherein the
control system is adapted to analyze the image data and verify that
the tissue retainer is within design tolerances for the selected
configuration.
[0156] The laser-machining system of paragraph 126, further
comprising a stabilization device adapted to stabilize the suture
thread adjacent the selected location.
[0157] The laser-machining system of paragraph 126, further
comprising a stabilization device adapted to stabilize the suture
thread adjacent the selected location without mechanical contact
with the suture thread.
[0158] The laser-machining system of paragraph 126, further
comprising a fluid bearing adapted to stabilize the suture thread
adjacent the selected location.
[0159] The laser-machining system of paragraph 126, 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.
[0160] The laser-machining system of paragraph 126, wherein:
[0161] the optic subsystem includes one or more axicon prisms.
[0162] The laser-machining system of paragraph 126, wherein:
[0163] the laser beam has a Gaussian power density
distribution.
[0164] The laser-machining system of paragraph 126, wherein:
[0165] the laser beam has a ring-shaped power density distribution
of selectable ring diameter.
[0166] A stabilization device for contactless stabilization of a
suture thread in a region of the suture thread, wherein the
stabilization device comprises:
[0167] a source of pressurized fluid; and
[0168] 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.
[0169] The stabilization device of paragraph 140, wherein:
[0170] the fluid outlet is nozzle-shaped.
[0171] The stabilization device of paragraph 140, wherein:
[0172] the suture thread passes through the fluid outlet.
[0173] The stabilization device of paragraph 140, wherein the
stabilization device comprises:
[0174] 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;
[0175] a suture inlet connected to the fluid manifold; and
[0176] 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.
[0177] The stabilization device of paragraph 140 in combination
with a machining system adapted to direct a laser beam at the
suture thread to create a tissue retainer in the region of the
suture thread.
[0178] The stabilization device of paragraph 140, in combination
with a laser-machining system comprising:
[0179] a laser subsystem adapted to provide a laser beam,
[0180] an optic system adapted to receive the laser beam and
generate a focused laser beam directed at a volume of the suture
thread,
[0181] a transport subsystem adapted to move the suture thread
relative to the laser beam,
[0182] an imaging subsystem adapted to image the suture thread and
generate image data; and
[0183] a control subsystem adapted to control the laser subsystem
and transport subsystem to create a tissue retainer of a selected
configuration in the region of the suture thread.
[0184] A method for creating a self-retaining suture comprising:
[0185] (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; [0186] (b) directing a laser
beam at a selected volume of suture material within the selected
region of the suture thread; [0187] (c) removing the selected
volume of the suture material from within the selected region of
the suture thread to create a tissue retainer; [0188] (d) repeating
steps (a), (b) and (c) for a plurality of selected regions of the
suture thread to create a plurality of tissue retainers.
[0189] The method of paragraph 146, further comprising: [0190] (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.
[0191] A laser-machining system adapted to make tissue retainers on
a suture thread, wherein the laser-machining system comprises:
[0192] a laser subsystem adapted to provide a laser beam;
[0193] an optic system adapted to receive the laser beam and
generate a focused laser beam directed at a volume of the suture
thread;
[0194] a transport subsystem adapted to move the suture thread
relative to the focused laser beam;
[0195] a marking subsystem adapted to change a visual
characteristic of a selected region of the suture thread without
ablating suture material; and
[0196] a control subsystem adapted to control the laser subsystem,
marking subsystem, and transport subsystem to create a tissue
retainer of a selected configuration at a selected location on said
suture thread and create a visible marker on the suture thread at a
different selected location on said suture thread.
[0197] A method for making a self-retaining suture comprising;
[0198] (a) identifying a tissue retainer location on the suture
thread; [0199] (b) providing a laser beam; [0200] (b) directing a
laser beam at a portion of the tissue retainer location on the
suture thread; [0201] (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; [0202] (d)
repeating steps (a), (b) and (c) to generate a plurality of tissue
retainers on the suture thread; and [0203] (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.
[0204] The method of paragraph 149, further comprising: [0205] (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.
[0206] The method of paragraph 149, wherein step (e) comprises
treating the self-retaining suture with heat to elevate the tips of
the plurality of tissue retainers so that the tips protrude from
the suture thread.
[0207] The method of paragraph 149, wherein step (e) comprises
treating the self-retaining suture with tension to elevate the tips
of the plurality of tissue retainers so that the tips protrude from
the suture thread.
[0208] The method of paragraph 149, wherein step (e) comprises
treating the self-retaining suture with heat and tension to elevate
the tips of the plurality of tissue retainers so that the tips
protrude from the suture thread.
[0209] A method for making a self-retaining suture comprising;
[0210] (a) providing a suture thread having a surface; [0211] (b)
identifying a first volume of suture material on the surface of the
thread; [0212] (c) identifying a second volume of suture material
from within the first volume of suture material; [0213] (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 [0214] (e)
repeating steps (b), (c) and (d) to generate a plurality of tissue
retainers protruding from the suture thread.
[0215] The method of paragraph 154, 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.
[0216] The method of paragraph 154, 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.
[0217] The method of paragraph 154, wherein:
[0218] step (c) comprises identifying a conical subvolume of suture
material from within the volume of suture material wherein the
subvolume of suture material; and
[0219] 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.
[0220] The method of paragraph 154, wherein step (a) comprises
providing a suture thread having a surface and a noncircular
cross-section.
[0221] The method of paragraph 154, wherein:
[0222] step (a) comprises providing a suture thread having a
surface and a plurality of longitudinal ridges noncircular
cross-section; and
[0223] step (b) comprises identifying a first volume of suture
material on the surface of the thread within one of the
longitudinal ridges.
[0224] The method of paragraph 154, wherein:
[0225] step (a) comprises providing a suture thread having a
surface and a polygonal cross section having a plurality of
longitudinal apices; and
[0226] step (b) comprises identifying a first volume of suture
material on the surface of the thread including one of the
longitudinal apices.
[0227] Although the present invention has been shown and described
in detail with regard to only a few exemplary embodiments of the
invention, it should be understood by those skilled in the art that
it is not intended to limit the invention to the specific
embodiments disclosed. Various modifications, omissions, and
additions may be made to the disclosed embodiments without
materially departing from the novel teachings and advantages of the
invention, particularly in light of the foregoing teachings.
Accordingly, it is intended to cover all such modifications,
omissions, additions, and equivalents as may be included within the
spirit and scope of the invention as defined by the following
claims.
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