Surgical suture abstract
A multifilament surgical suture has an end portion tipped with
cyanoacrylate resin. The suture can also include filling agents
and lubricants which are incorporated into the suture prior to the
suture being tipped. A typical filling agent is glycerol. A typical
lubricant includes a copolymer of glycolide and lactide. Tipping
is accomplished by passing a portion of the suture through a mist
of monomeric cyanoacrylate resin and allowing the resin to harden
by curing. The tipped portion may then be cut to create a tipped
end for insertion into a surgical needle.
Surgical suture claims
What is claimed is:
1. In a length of multifilament surgical suture, the improvement
comprising at least one end of said multifilament surgical suture
tipped with substantially fully cured cyanoacrylate.
2. The suture of claim 1 wherein said surgical suture is a filled
3. The suture of claim 2 wherein said suture is filled with a glycerol
4. The suture of claim 1 wherein said suture is coated with at
least one lubricant coating.
5. The suture of claim 4 wherein said lubricant coating is a copolymer
of glycolide, lactide and polyethylene oxide.
6. In a length of multifilament surgical suture coated with a lubricant
coating; the improvement comprising at least one end of said coated
multifilament surgical suture tipped with substantially fully cured
7. The suture of claim 6 wherein said surgical suture is a filled
8. The suture of claim 6 wherein said suture is filled with a glycerol
9. The suture of claim 6 wherein said lubricant coating is a copolymer
of glycolide, lactide and polyethylene oxide.
Surgical suture description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a tipped surgical suture and a method
and apparatus for making same and a combined tipped suture and surgical
needle. In particular, it relates to a cyanoacrylate tipping agent
for braided sutures to prevent brooming and to increase stiffness,
thereby facilitating attachment of the suture to a surgical needle.
2. Background of the Art
For many years, surgeons have employed needle-suture combinations
in which a suture or ligature is attached to the shank end of a
needle. Such needle-suture combinations are provided for a wide
variety of monofilament and braided suture materials, both absorbable
and non-absorbable, e.g., catgut, silk, nylon, polyester, polypropylene,
linen, cotton, and absorbable synthetic materials such as polymers
and copolymers of glycolic and lactic acid.
Needle-suture combinations fall into two general classes: standard,
or non-detachable, needle attachment and removable, or detachable,
needle attachment. In the case of standard needle attachment, the
suture is securely attached to the needle and is not intended to
be separable therefrom, except by cutting or severing the suture.
Removable needle attachment, by contrast, is such that the needle
is separable from the suture in response to a force exerted by the
surgeon. Minimum acceptable forces required to separate a needle
from a suture (for various suture sizes) are set forth in the United
States Pharmacopoeia (USP). As to detachable needles, the United
States Pharmacopoeia prescribes minimum individual pull-out forces
and minimum average pull-out forces as measured for five needle-suture
combinations. The minimum pull-out forces for both standard and
removable needle-suture attachment set forth in the United States
Pharmacopoeia are hereby incorporated by reference.
One typical method for securing a suture to a needle involves providing
a cylindrical recess in the shank end of a needle and securing a
suture therein. For example, U.S. Pat. No. 1558037 teaches the
addition of a cement material to such a substantially cylindrical
recess to secure the suture therein. Additional methods for bonding
a suture within a needle bore are described in U.S. Pat. Nos. 2928395
(adhesives) and 3394704 (bonding agents). Alternatively, a suture
may be secured within an axial bore in a needle by swaging the needle
in the region of the recess. See, e.g., U.S. Pat. No. 1250114.
Additional prior art methods for securing a suture within a needle
bore include expansion of a catgut suture through the application
of heat (U.S. Pat. No. 1665216), inclusion of protruding teeth
within the axial bore to grasp an inserted suture (U.S Pat. No.
1678361) and knotting the end of the suture to be inserted within
the bore to secure the suture therein (U.S. Pat. No. 1757129).
Methods for detachably securing a suture to a needle are also well
known. For example, U.S. Pat. Nos. 3890975 and 3980177 teach
swaging a suture within a needle bore such that the suture has a
pull-out value of 3 to 26 ounces. Alternative detachable attachment
methods include providing a weakened suture segment (U.S. Pat. No.
3949756), lubricant tipping the end of a suture to be inserted
in the axial bore of a needle (U.S. Pat. No. 3963031) and pre-tensioning
a suture that is swaged within an axial needle bore (U.S. Pat. No.
3875946). See also, U.S. Pat. Nos. 3799169; 3880167; 3924630;
3926194; 3943933; 3981307; 4124027; and, 4127133.
Another method for attaching a suture to a needle involves the
use of tubing which is secured to the shank end of the needle and
to the suture. For example, U.S. Pat. No. 1613206 describes the
use of a tubing (preferably silver) which is secured to the shank
end of a needle and to a ligature. It is suggested that the tube
may be attached to the needle by pressure or soldering and to the
ligature by pressure or cementing. It is also suggested that the
shank of the needle be of reduced cross section and that the furthest
extremity of the reduced diameter shank section be provided with
a spike or point upon which the suture may be secured prior to tube
U.S. Pat. No. 2240330 describes a tubing attachment method whereby
the tubing and suture are releasably secured to the needle. In particular,
the needle and tubing are provided with cooperating catch and abutment
means which are released one form the other by rotating the needle
90.degree. relative to the tubing (or vice versa). The tubing is
manufactured from spring-tempered carbon steel or chrome nickel
steel and is secured to the suture by heating the tubing and then
swaging to the suture.
U.S. Pat. No. 3311100 related to a flexible composite suture
having a tandem linkage. The needle is secured to a flexible suture
leader manufactured from a readily sterilizable plastic such as
nylon, linear polyethylene, isostatic polypropylene, polyester,
silk or other proteinaceous material, e.g., by inserting and crimping
the leader within an axial bore in the needle shank. The opposite
end of the suture leader is crimped within a connector sleeve of
a thin walled metal tubing, e.g., stainless steel. The opposite
end of the tubing is crimped around a steel suture, e.g., monofilament
U.S. Pat. No. 3918455 describes a needle-suture attachment wherein
a hollow suture portion is secured to the shank end of a needle
which is of reduced cros-section as compared to the remainder of
Additional patents which describe the use of tubing to effect suture-needle
attachment include U.S. Pat. Nos. 4672734 (forming needle from
U-shaped metal plate around suture), 4359053 (silicone tubing),
3835912 (laser welding of metal tube to needle), 2814296 2802468
(chamfered tubing ends), 2302986 2240330 1981651 (needle
and tubing screw threaded), 1960117 and 1591021.
In addition to the needle-suture constructions of the aforedescribed
pull-out variety, it is known from U.S. Pat. No. 4805292 to provide
a needle-suture combination in which a suture cutting edge is formed
at the shank end of the needle. However, the combined needle-suture
device of U.S. Pat. No. 4805292 like others described above,
possesses a suture tip-receiving axial bore, or recess, formed in
the butt end of the needle and as such is subject to the disadvantages
recounted above which are associated with a needle possessing an
Insertion of sutures into a hole, recess or tube for attachment
to surgical needles presents problems peculiar to suture needle
combinations. Braided multifilament sutures in particular are difficult
to insert into the very small aperture of a surgical needle: unless
modified, they are too limp for the suture tip to be controlled
for insertion and they have a tendency to "broom", i.e.,
the filaments have a tendency to flare out at the cut end so that
the diameter of the cut end exceeds the diameter of the needle hole.
Various techniques have been employed to modify sutures to overcome
the problems of limpness and brooming. One known method employs
a tipping agent, which is a material used to coat the suture to
stiffen the filaments and adhere them together.
Typically, a suture to be tipped is first placed under tension
to reduce slack so that the suture may be maintained in a predetermined
position on a frame or rack or other suture holding device. Optionally,
the tension may be such as to reduce the diameter of the suture.
See Canadian Patent No. 1009532. The suture is then dipped into
the tipping solution and allowed to dry while under tension. The
sutures are then dried, such as by being warmed in a drying oven
at about 225.degree. F. for about 10 minutes. After drying the sutures
can be cut and released from tension. The process results in a tipped
end on each side of a cut. Where tension has optionally been employed
to reduce the suture diameter, release of said tension will allow
the suture to expand to its original diameter except at the tipped
end portion. This can facilitate insertion of the end into a needle.
Tipping agents may be dissolved in solvents to form dipping solutions.
By way of example, Mariotte mixture is a dipping solution comprising
nylon dissolved in isopropyl alcohol. Other polymers and solvents
may also be used. Gould mixture is a dipping solution comprising
nylon dissolved in methanol. At least one major manufacturer of
surgical needles recommends use of Mariotte mixture or Gould mixture
for tipping sutures. A multitude of other tipping agents, including
polymers and solvents, have been proposed. For example McGregor
U.S. Pat. No. 3890975 discloses coating the suture with a binding
resin or adhesive. The composition may be any non-toxic adhesive
composition, either organic, inorganic or a hybrid. Suitable organic
materials are such natural products as starch, dextrin, asphalt,
animal and vegetable proteins, natural rubber, shellac, semi-synthetic
products such as cellulose nitrate and the other cellulosics, polyamides
derived from dimer acids, castor-oil based polyurethanes; such well-known
synthetic resins as vinyl-type addition polymers, both resins and
elastomers; polyvinyl acetate, polyvinyl alcohol, acrylics, unsaturated
polyesters, butadiene/acrylonitrile, butadiene/styrene, neoprene,
butyl rubber, polyisobutylene; and polymers formed by condensation
and other step-wise mechanisms, i.e., epoxies, polyurethanes, polysulfide
rubbers, and the reaction products of formaldehyde with phenol,
resorcinol, urea, and melamine. McGregor states that particularly
preferred bonding compositions are epoxide resins and polyester
Schmitt U.S. Pat. No. 3736646 discloses that it is known to tip
braided sutures by dipping the end of the suture in a plastic such
as a solution in isopropyl alcohol. Schmitt suggests that for absorbable
sutures an absorbable tipping agent is desirable, and proposes that
a copolymer of lactic and glycolic acid dissolved in a suitable
organic solvent, such as xylene or toluene, be applied to tip the
Nichols U.S. Pat. No. 2734506 discloses a dipping solution of
polymers of methacrylic acid esters in an organic solvent such as
toluene, xylene acetone, ethyl acetate, methylethyl ketone, or naphtha.
Shepherd et al. U.S. Pat. No. 3849185 discloses the use of an
acrylic casting syrup as a tipping agent, the syrup being fully
polymerized after being applied to the suture.
In addition, paraffin/hexane solution (10% paraffin) has been used
as a suture coating agent as well as Arrochem (TM), a nylon resin
plus methanol composition manufactured by ArroChem, Inc. of 201
Westland Farm Road, Mt. Holly, NC 28120 and SILASTIC (TM) Medical
Adhesive (a silicon elastomer composition manufactured by Dow Corning
Although dipped sutures prepared in accordance with the above procedures
may have been used successfully, there are several drawbacks with
the use of tipping solutions. The main problems relate to tipping
consistency and process control. Non-uniform solvent evaporation,
which may be caused by variations in the solvent, oven temperature
and heating time can result in inconsistent tipping. Furthermore,
the dried residue of polymer left after evaporation can flake off
or develop cracks.
Another method which has been employed for treating sutures involves
melt fusion, as described in U.S. Pat. No. 4832025 issued to
Coates. The suture is . heated to a temperature at least high enough
to "melt fuse"
a portion of the outer filaments of the suture. According to Coates,
such temperature is typically about 260.degree. C. to 300.degree.
C. (500.degree. F. to 572.degree. F). Exposure of synthetic sutures
to such extreme temperatures melt fuses the filaments, and the melt
fused suture portion stiffens upon cooling. Melting of the filaments
has the effect of holding the filaments together when the suture
is cut. It also causes stiffening of the suture which facilitates
insertion of the suture end into the drilled hole of a needle. However,
the melt fusion of suture has significant drawbacks.
Firstly, the melt fusion of filaments weakens the suture, whose
tensile strength is degraded in proportion to the extent of melt
Secondly, melt fusion causes an irreversible change in the filaments
which result in permanent stiffening and permanent loss of tensile
Thirdly, with the extreme temperatures disclosed by Coates for
melt fusion an inconveniently short heating cycle is required. For
example, for a size 3/0 silicone coated polyester suture heated
to between 260.degree. C. to 300.degree. C. in a 4 mm. diameter
eating tunnel, the heating time is no more than about 3 seconds.
Such short heating times make it difficult to control the process
and leads to inconsistencies and variations in the melt fused tipping
A further consideration pertinent to suture tipping is that sutures
are often prepared with lubricant coatings such as silicone or fatty
acid salts in order to increase lubricity and to improve "tie-down"
performance, i.e., the ease of sliding a knot down the suture into
place. Such lubricant coatings typically are incompatible with the
materials and methods currently employed for tipping sutures. In
particular, prior known tipping agents do not adhere well to lubricant
coated sutures, which may result in inconsistent tipping or an undesirable
reduction of suture-needle pull out force. The melt fusing method
of tipping may destroy the lubricant coating or render it less effective
in areas away from the needle.
A method of and apparatus for tipping surgical sutures has been
discovered which may be used to tip both uncoated and coated sutures
and which provides superior stiffening of the suture for insertion
into an opening to attach the suture to a needle.
SUMMARY OF THE INVENTION
A surgical suture tipped with cyanoacrylate and a process for tipping
with cyanoacrylate are disclosed. In addition, a method and apparatus
are provided herein for handling and tipping a surgical suture.
In the preferred embodiment a suture is wound around a drum while
its diameter is continuously monitored in the x and y directions,
with the tension on the suture continuously being adjusted to consistently
control the diameter of the suture as it is wound onto the drum.
The drum is then placed in an apparatus which passes selected portions
of the suture through a mist of cyanoacrylate tipping agent generated
by sonic or ultrasonic atomization. The tipping agent quickly cures
as it polymerizes in response to ambient residual moisture to stiffen
the coated portion of the suture. The coated portion of the suture
may be cut to create at least one tipped end for insertion into
a surgical needle. To assure consistent repeated processing the
atomization apparatus is flushed before and after each cycle with
nitrogen in order to prevent curing of the cyanoacrylate in the
apparatus, which would undesirably interfere with proper operation
of apparatus. Advantageously, cyanoacrylate tipping in accordance
with the invention can be used effectively to tip all types of sutures,
including filled sutures and sutures coated with lubricants and
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partially cutaway side view illustrating a surgical
needle and suture combination.
FIG. 2 is an exploded perspective view illustrating a surgical
needle in conjunction with a suture.
FIG. 3 is a partially cutaway side view illustrating a surgical
needle in combination with a suture.
FIG. 4 is a diagrammator illustration of the suture winding system
of the present invention.
FIG. 5 is a side elevational view of the suture winding apparatus
of the present invention.
FIG. 6 is a perspective view of the suture winding drum of the
FIG. 6A is an end view of a rib configuration associated with the
suture winding drum.
FIGS. 6B and 6C show end elevational views of drums having 2 and
3 notches, respectively.
FIG. 7 is a side view of the suture retaining clamp of the present
FIG. 8 is a perspective view of the main support of the suture
FIG. 9 is a perspective view of the dowel arm support of the present
FIG. 10 is a perspective view of the dowel arm of the present invention.
FIG. 11 is a perspective view of the rocker clamp support of the
FIG. 12 is a perspective view of the rocker clamp of the present
FIG. 13 is a perspective view of the rocker spring of the present
FIG. 14 is a perspective view of the suture tipping apparatus of
the present invention.
FIG. 15 is a cut away front elevational view of the suture tipping
apparatus of the present invention. FIG. 16 is a cut away side elevational
view of the suture tipping apparatus of the present invention.
FIG. 17 is a front sectional view of the spray head assembly of
the suture tipping apparatus.
FIG. 18 is a partially cut away side view of the spray head assembly
of the suture tipping apparatus.
FIG. 19 is a perspective view of a suture with a tipped portion.
FIG. 20 is a schematic illustration of the suture tipping system
of the present invention.
FIG. 21 illustrates the placement of clamps on the drum to secure
the suture for a cutting procedure.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The present invention is generally directed to tipping surgical
sutures with cyanoacrylate in order to stiffen the suture tip and,
as to multifilament sutures, prevent brooming. Tipping the suture
with cyanoacrylate facilitates insertion of the suture tip into
an opening for attachment to a suture. Advantageously, the cyanoacrylate
tipping is compatible with a broad range of sutures and coatings,
and a novel method and apparatus have been developed for applying
cyanoacrylate to sutures in an atomized spray. Because the cyanoacrylate
tipping agent and process are applicable to a wide range of materials
and needle suture attachment methods, suture constructions and general
methods of tipping sutures will be discussed prior to discussing
the preferred apparatus for spray tipping.
The present invention is primarily directed to the treatment of
braided surgical sutures. The term "braid" means a substantially
symmetrical strand formed by crossing a number (at least three)
of individual strands composed of one or more filaments diagonally
in such manner that each strand passes alternatively over and under
one or more of the others. The braid may be of traditional tubular
braid construction or spiroid braid construction and may include
a core section composed of one or more filaments around which the
braid is externally fabricated.
The braided suture can be fabricated from a wide variety of natural
and synthetic fibrous materials such as any of those heretofore
disclosed for the construction of sutures. Such materials include
non-absorbable as well as partially and fully bio-absorbable (i.e.,
resorbable) natural and synthetic fiber-forming polymers. Non-absorbable
materials which are suitable for fabricating braided sutures include
silk, polyamides, polyesters such as polyethylene terephthalate,
polypropylene, silk cotton, linen, etc. Carbon fibers, steel fibers
and other biologically acceptable inorganic fibrous materials can
also be employed. Bio-absorbable sutures may be fabricated from
natural collagenous material or synthetic resins including those
derived from glycolic acid, glycolide, lactic acid, lactide, dioxanone,
polycaprolactone, epsilon-caprolactone, trimethylene carbonate,
etc., and various combinations of these and related monomers. Sutures
prepared from resins of this type are known in the art.
Braided multifilament sutures typically are coated with one or
more coating compositions to improve functional properties such
as surface lubricity and knot tie-down behavior. A variety of suture
coating compositions proposed for either or both of these purposes
are well known in the art, e.g., those disclosed in U.S. Pat. Nos.
3867190; 3942532; 4047533; 4452973; 4624256; 4649920;
4716203; and 4826945.
A preferred lubricant coating is a bioabsorbable coating composition
obtained by copolymerizing in accordance with known procedures (1)
a polyether glycol selected from the group consisting of relatively
low molecular weight polyalkylene glycol, e.g., one corresponding
to the general formula HO(RO),H wherein R is an alkylene group of
from 2-4 carbon atoms and y is an integer of from about 100-350
and polyethylene oxide-polypropylene oxide block copolymer, e.g.,
one corresponding to the general formula H(OCH.sub.2 CH.sub.2).sub.x
(OC.sub.3 H.sub.6).sub.y (OCH.sub.2 CH.sub.2).sub.z OH wherein x
is,an integer of from about 45-90 y is an integer of from about
60-85 and z is an integer of from about 45-90 with (2) a mixture
of lactide monomer and glycolide monomer or a preformed copolymer
of lactide an glycolide, the weight ratio of (1) to (2) preferably
ranging from about 4:1 to about 1:4 and more preferably from about
2:1 to about 1:2. The ratio of lactide to glycolide in the monomer
mixture or in the copolymer of these monomers preferably varies
from. about 65-90 mole percent lactide and 10-35 mole percent glycolide.
Polyether glycols having molecular weights of about 3500-25000
and preferably from about 4000-10000 and polyethylene oxide-polypropylene
oxide block copolymers having molecular weights of from about 4000-10000
and preferably from about 7500 to about 9000 e.g., those disclosed
in U.S. Pat. Nos. 2674619 3036118 4043344 and 4047533
and commercially available as they Pluronics (BASF-Wyandotte). Where
preformed copolymers of lactide and glycolide are employed in preparing
the bioabsorbable coating compositions, they may be prepared as
described in U.S. Pat. No. 4523591.
The amounts of bioabsorbable coating composition to be applied
to the suture, e.g., by coating, dipping, spraying or other appropriate
techniques, will vary depending upon the specific construction of
the suture, its size and the material of its construction. In general,
the coating composition applied to an unfilled suture will constitute
from about 1.0 to about 3.0 percent by weight of the coated suture,
but the amount of coating add on may range from as little as about
0.5 percent, by weight, to as much as 4.0 percent or higher. For
a preferred filled (i.e. containing a storage stabilizing agent)
braided suture, amounts of coating composition will generally vary
from about 0.5% to about 2.0% with as little as 0.2% to as much
as 3.0%. As a practical matter and for reasons of economy and general
performance, it is generally preferred to apply the minimum amount
of coating composition consistent with good surface lubricity and/or
knot tie-down characteristics and this level of coating add on is
readily determined experimentally for any particular suture.
Recently it has been proposed to also apply to an absorbable braided
suture a storage stabilizing amount of a filler material containing
at least one water soluble liquid polyhydroxy compound and/or ester
thereof. In addition to laving an enhanced degree of storage stability,
a braided suture which has been filled with a storage stabilizing
amount of, e.g., glycerol, exhibits better flexibility and "hand"
characteristics than the untreated suture. Moreover, since the polyhydroxy
compounds are generally capable of dissolving a variety of medico-surgically
useful substances, they can be used as vehicles to deliver such
substances to a wound or surgical site at the time the suture is
introduced into the body.
The useful .storage stability agents are generally selected from
the water soluble, liquid polyhydroxy compounds and/or esters of
such compounds, preferably those having no appreciable toxicity
for the body at the levels present. The expression "liquid
polyhydroxy compound" contemplates those polyhydroxy compounds
which in the essentially pure state are liquids, as opposed to solids,
at or about ambient temperature, e.g., at from about 15.degree.
C. to about 40.degree. C. The preferred polyhydroxy compounds possess
up to about 12 carbon atoms and where the esters are concerned,
are preferably the monoesters and diesters. Among the specific storage
stabilizing agents which can be used with generally good results
are glycerol and its mono-and diesters derived from low molecular
weight carboxylic acids, e.g., monoacetin and diacetin (respectively,
glyceryl monoacetate and glyceryl diacetate), ethylene glycol, diethylene
glycol, triethylene glycol, 13-propanediol, trimethylolethane,
trimethylolpropane, pentaerythritol, sorbitol, and the like. Glycerol
is especially preferred. Mixtures of storage stabilizing agents,
e.g., sorbitol dissolved in glycerol, glycerol combined with monoacetin
and/or diacetin, etc., are also useful.
To prevent or minimize run-off or separation of the storage stabilizing
agent from the suture, a tendency to which relatively low viscosity
compounds such as glycerol are especially prone, it can be advantageous
to combine the agent with a thickener. Many kinds of pharmaceutically
acceptable non-aqueous thickeners can be utilized including water-soluble
polysaccharides, e.g., hydroxypropyl methycellulose (HPMC), and
the other materials of this type which are disclosed in European
Patent Application 0 267 015 referred to above, polysaccharide gums
such as guar, xanthan, and the like, gelatin, collagen, etc. An
especially preferred class of thickeners are the saturated aliphatic
hydroxycarboxylic acids of up to about 6 carbon atoms and the alkali
metal and alkaline earth metal salts and hydrates thereof. Specific
examples of such compounds include salts of lactic acid such as
calcium lactate and potassium lactate, sodium lactate, salts of
glycolic acid such as calcium glycolate, potassium glycolate and
sodium glycolate, sales of 3-hydroxy propanoic acid such as the
calcium, potassium and sodium salts thereof, salts of 3-hydroxybutanoic
acid such as calcium, potassium and sodium
salts thereof, and the like. As stated hereinabove, hydrates of
these compounds Call also be used. Calcium lactate, especially calcium
lactate pentahydrate, is a particularly preferred thickener.
When a thickener is utilized, it will be incorporated in the filling
composition in at least that amount required to increase the overall
viscosity of the storage stabilizing agent to the point where the
agent no longer readily drains away from the suture in a relatively
short period. In the case of a preferred storage stabilizing agent-thickener
combination, namely, glycerol and calcium lactate, the weight ratio
of glycerol to calcium lactate can vary from about 1:1 to about
10:1 and preferably is from about 6:1 to 8:1.
If necessary or desirable, the storage stabilizing agent together
with optional thickener can be dissolved in any suitable non-aqueous
solvent or combination of solvents prior to use. To be suitable,
the solvent must (1) be miscible with the storage stabilizing agent
and optional thickener, if present (2) have a sufficiently high
vapor pressure to be readily removed by evaporation, (3) not appreciably
affect the integrity of the suture and (4) be capable of wetting
the surface of the suture. Applying these criteria to a preferred
storage stabilizing agent, glycerol, advantageously in admixture
with a preferred thickener, calcium lactate, lower alcohols such
as methanol and ethanol are entirely suitable solvent carriers.
When a solvent is utilized in the preparation of the stabilizing
agent, e.g., methanol, such solvent can be employed in amounts providing
a solution concentration of from about 20% to about 50%, preferably
about 30% to about 45%, by weight
of the storage stabilizing agent including any optional thickener.
As stated, a braided suture may be impregnated with one or more
medico-surgically useful substances, e.g., those which accelerate
or beneficially modify the healing process when the suture is applied
to a wound or surgical site. So, for example, the braided suture
herein can be provided with a therapeutic agent which will be deposited
at the sutured site. The therapeutic agent can be chosen for its
antimicrobial properties, capability for promoting wound repair
and/or tissue growth or for specific indications such as thrombosis.
Antimicrobial agents such as broad spectrum antibiotics (gentamicin
sulphate, erythromycin or derivatized glycopeptides) which are slowly
released into the tissue can be applied in this manner to aid in
combating clinical and sub-clinical infections in a surgical or
trauma wound site.
To promote wound repair and/or tissue growth, one or more biologically
active materials known to achieve either or both of these objectives
can be applied to the braided suture of the present invention. Such
materials include any of several human Growth factors (HGFs), magainin,
tissue or kidney plasminogen activator to cause thrombosis, superoxide
dismutase ot scavenge tissue damaging free radicals, tumor necrosis
factor for cancer therapy, colony stimulating factor, interferon,
interleukin-2 or other lymphokine to enhance the immune system,
and so forth.
The filling composition can contain one or more additional components
which promote or enhance the wound healing effectiveness of the
HGF component. Thus, e.g., site-specific hybrid proteins can be
incorporated in the
filling composition to maximize the availability of the HGF at
the wound site and/or to potentiate wound healing. See e.g., Tomlinson
(Ciba-Geigy Pharmaceuticals, West Sussex, U.LK.), "Selective
Delivery and Targeting of Therapeutic Proteins", a paper presented
at a symposium held Jun. 12-14 1989 in Boston, MA, the contents
of which are incorporated by reference herein. The HGFs can also
be associated with carrier proteins (CPs), e.g., in the form of
CP-bound HGF(s), to further enhance availability of the HGF(s) at
a wound site as disclosed in "Carrier Protein-Based Delivery
of Protein Pharmaceuticals", a paper of Biogrowth, Inc., Richmond,
CA presented at the aforementioned symposium, the contents of said
paper being incorporated by reference herein. The HIGFs can also
be incorporated in liposomes to provide for their release over an
extended period. Lactate ion can be present to augment the wound
healing activity of the HIGF. Protectants for the HGF can also be
utilized, e.g., polyethylene glycols, acetoxyphenoxy polyethoxy
ethanols, polyoxyethylene sorbitans, dextrans, albumin, poly-D-alanyl
peptides and N-(2-hydroxypropyl)-methacrylamide (HPMA).
As stated previously, prior known tipping methodologies are not
fully compatible with a suture or its coatings, fillers, therapeutic
agents, antimicrobial agents and/or biologically active materials,
either because the tipping agent will not adhere properly or because
the methodology (such as melt fusing) results in deterioration of
the suture, its coatings, additives, and fillers.
The suture tipping agent and method of the present invention are
compatible with and may be used on any type of surgical suture including
multifilament bioabsorbable or non-bioabsorbable sutures. Advantageously,
the tipping agent and method of the invention are applicable to
all types of multifilament braided sutures, including those which
contain one or more fillers, coatings, etc.
In practice, a segment of the suture is selected for tipping and
may be of any length appropriate for inserting a suture end cut
from such segment into an opening, such as the barrel end of a surgical
needle, to facilitate attachment of the suture to the needle.
Typically the suture is placed under sufficient tension to take
up slack. Additional tension may be applied to reduce the suture
diameter, if desired, to result in a tipped section of reduced diameter
relative to the remainder of the suture.
A stiffening or "tipping" agent is then applied to the
selected segment of suture. The stiffening agent is a cyanoacrylate
monomer such as methyl 2-cyanoacrylate, or ethyl 2-cyanoacrylate.
The preferred cyanoacrylate is available under the name LOCTITE(TM)
Medical Device Adhesive 18014 and is available from the Loctite
Corporation, 705 N. Mountain Road, Newington, CT 06111. The preferred
Loctite Medical Device Adhesive is a moisture activated polymer
which comprises 99+% ethyl cyanoacrylate and small amounts of hydroquinone
and organic anhydride. It has a specific gravity of 1.05 and a
boiling point greater than 300.degree. F. The cyanoacrylate monomer
may be applied in a variety of ways, such as dipping or brushing
and preferably is applied by spraying, as described below. Upon
contact with the suture, the residual moisture of the suture and
surrounding environment catalyzes the polymerization of the cyanoacrylate
almost instantly. The polymerized cyanoacrylate stiffens the segment
of the suture by coating the individual filaments of the suture
with a relatively stiff coating, and, because the cyanoacrylate
is an adhesive, the individual filaments are bonded together to
prevent brooming. A further advantage of the ethyl cyanoacrylate
tipping agent is that it is bioabsorbable and will not leave a permanent
residue in body tissue. Because the cyanoacrylate polymerizes almost
instantly, the tipping agent is stiffened immediately without any
additional drying or curing steps. This has the added advantage
of reducing processing steps and accompanying handling and equipment
requirements. In the preferred spray tipping process, polymerization
is substantially complete by the end of the apparatus cycle and
the tipped suture may be further processed without delay.
The next step is cutting the stiffened segment to create at least
one "tipped" end for connecting to the end of a surgical
needle. Two tipped ends of the suture may be desirable for attaching
a needle to each end of the suture to provide a so-called double
armed suture. The coated segment may be cut with scissors, a razor
blade, or by a knife edge moving transverse to the direction of
the tipped suture segment, or by any other suitable means.
The tipped end is now ready to be connected to the surgical needle.
One method of connection, illustrated in FIG. 1 requires a needle
1 with a barrel end having an axial aperture 1a. The tipped end
of suture 2 is inserted into the aperture 1a and the end of the
needle may then be swaged, crimped or otherwise constricted to grip
and hold the suture, either permanently or with a pull-out force
defined by U.S.P. for detachable needles. The swage or crimp method
of attachment is conventional and well known in the art.
Another method of attaching the suture to the needle is illustrated
in FIG. 2 wherein the barrel end of the needle 1 has a cylindrical
portion 1b of lesser diameter than the needle and extending axially
from the needle 1. The "tipped" or stiffened end 2a of
suture 2 is positioned adjacent portion 1b and extends axially through
the bore of a tube 3 which is positioned around the junction of
tipped end 2a and needle portion 1b. Tube 3 is made of a material
capable of shrinking or undergoing contraction upon application
of energy, e.g., heat. Suitable materials include "memory based
metals," e.g., nickel-iron-titanium mixtures, or copper based
materials, as are well known in the art (see, e.g., U.S. Pat. Nos.
3759552 3801954 4198081 and 4733680), and shrinkable plastic
materials, such as polyvinylidene fluoride materials available from
Raychem Corporation, Menlo Park, Calif., under the tradename Kynar.
One such polyvinylidene fluoride material available from Raychem
Corporation is RT-850. In the case of shrinkable plastic materials,
the tubing typically is extruded such that the inner diameter is
less than the final desired diameter, i.e., the inner diameter of
the tubing after energy application in the attachment method of
the present invention. Thereafter, the extruded tubing is expanded
radially outward through radial expansion means to provide a tubing
or expanded inner diameter. Such plastic tubing is thus adapted
to shrink or "recover" to its original extruded inner
diameter in response to the application of a predetermined amount
of energy. Suitable energy sources to accomplish shrinking of tubing
3 include heat (convective or conductive), radiation, microwave
Tube 3 is then subjected to energy, preferably consisting of heat,
in order to cause shrinkage or contraction of the tube such that
the inner surface of the tube bore grips both the needle portion
1a and the suture end 2a in the vicinity of the joint as shown in
FIG. 3. Alternatively, the tube may be attached to the needle and
suture sequentially, such as by first applying localized energy
to shrink the tube onto the needle shank and thereafter applying
energy to the remainder of the tube to shrink the tube into the
suture tip. Variations in the needle shank, such as tapering, contouring
or ribbing, may be used to increase gripping force of the tube to
the needle. Similarly, the relative gripping force of the tube on
the needle shank and suture may be varied by varying the length
of the tube section contacting each of the needle shank and suture.
In addition, tube 3 preferably is configured and dimensioned such
that when it is contracted the outer surface of the tube is substantially
flush or even with the outer surface of the needle. The gripping
force of the shrinkable tube 3 is sufficient to maintain the minimum
required pull out force for the suture, and may be adjusted to provide
either permanently attached or detachable suture needles. It has
been found that sutures, particularly coated and filled sutures,
tipped in accordance with the method of the present invention have
significantly higher pull out forces.
Attempts were made to tip coated sutures, such as silicone coated
Dacron.RTM. braided sutures, with polyurethane and epoxy adhesives.
These attempts did not result in any tipped sutures suitable for
attachment to needles.
COMPARATIVE EXAMPLES 1-2
Dacron.RTM. polyester 1-0 braided sutures coated with silicone
were tipped by swab application of (i) Arrochem composition; and
(ii) a "hot melt" 10% paraffin/hexane solution. Sutures
tipped with the 10% paraffin/hexane were further treated for 60
seconds in a heating apparatus set at 315.degree. F. The 10% paraffin/hexane
solution was difficult to work with since it had to be maintained
at about 130.degree. F. with constant stirring in order to maintain
the paraffin in solution. The tipped sutures were swaged to needles
in a conventional manner and pull-out force in both cases was measured
to be about 0.05 kg.
COMPARATIVE EXAMPLE 3
In an attempt to improve on the results of Comparative Examples
1-2 Dacron.RTM. polyester 1-0 braided sutures were placed in toluene
and brought to temperature of 80.degree.-82.degree. C. for ten minutes.
The total dwell time in toluene was approximately 20 minutes. The
washed sutures were tipped with 10% paraffin/hexane by swab application
and heated to 315.degree. F. for 60 seconds. The maximum pull-off
forces were approximately 0.05 kg, showing no improvement.
COMPARATIVE EXAMPLES 4-14
Dacron.RTM. polyester 1-0 braided sutures coated with silicone
were ultrasonically washed for five minutes in one of isopropyl
alcohol, TP10 Freon TF, hexane, xylene, and III-trichloromethane.
Samples of sutures washed by each method were tipped with Arrochem
solution and 10% paraffin/hexane (the paraffin/hexane tipped sutures
were heated to 315.degree. F. for 60 seconds, as before), resulting
in twelve types of differently treated and tipped sutures. The tipped
sutures were swaged to needles and the pull-out force was measured.
The pull-out forces of these sutures showed some improvement, having
pull-out forces of about 1.5 kg, but still did not achieve reliably
high pull-out forces.
COMPARATIVE EXAMPLES 15-16
Silicone coated Dacron.RTM. polyester 1-0 braided sutures were
wound on a paddle and soaked for five minutes in a 5% Mariotte mixture
solution (50 grams nylon in 946 ml. isopropyl alcohol and 150 ml.
water). Thereafter, the sutures were heated for 60 seconds at 315.degree.
F. and, after cooling, Arrochem solution was applied over the tip
previously treated with Mariotte mixture. No improvement in pull
out force was obtained, and the extended exposure to Mariotte mixture
was observed to have detrimental effects on the suture braid.
The above procedure was repeated using a 10 minute soak in Mariotte
mixture followed by heat treating for 10 minutes in an oven at 225.degree.
F, followed by tipping with Arrochem composition. No improvement
in pull-out force was observed when these sutures were attached
COMPARATIVE EXAMPLE 17
Silicone coated Dacron.RTM. polyester 1-0 braided sutures were
ultrasonically washed for 5 minutes in toluene and tipped with 10%
paraffin/hexane solution by swab application. The pull-off force
met U.S.P. minimums, e.g. 0.45 kg, but was still insufficient.
COMPARATIVE EXAMPLES 18-29
Silicone coated Dacron.RTM. polyester 1-0 braided sutures were
ultrasonically washed for 10 minutes in a variety of different washing
solutions, tipped by soaking for 5 minutes in either Arrochem or
5% Mariotte mixture, and attached to needles. The results are listed
below in Table I.
TABLE I ______________________________________ Pull-Off Cleaning
Solution Tipping Agent Force (kg) ______________________________________
18. Isopropyl alcohol Arrochem 0.05-1.0 19. Isopropyl alcohol Paraffin/Hexane
0.05-1.0 20. Freon T-F Arrochem 0.05-1.0 21. Freon T-F Paraffin/Hexane
0.05-1.0 22. Freon TP 10 Arrochem 0.05-1.0 23. Freon TP 10 Paraffin/Hexane
0.05-1.0 24. Trichloroethylene Arrochem 0.05-1.0 25. Trichloroethylene
Paraffin/Hexane 0.05-1.0 26. Xylene Arrochem 0.08-1.3 27. Xylene
Paraffin/Hexane 0.08-1.3 28. Hexane Arrochem 0.08-1.3 29. Hexane
Paraffin/Hexane 0.08-1.3 ______________________________________
COMPARATIVE EXAMPLES 30-33
Braided Dacron.RTM. polyester size 1-0 braided sutures were ultrasonically
washed in a toluene bath for 20 minutes. After solvent cleaning
the sutures were tipped by soaking for 5 minutes in one of (i) 10%
Silastic Medical Adhesive in hexane; (ii) 10% paraffin/hexane; (iii)
Arrochem solution; or (iv) Mariotte mixture. All the tipped sutures
were post-tipped at 315.degree. F. for 60 seconds. The tipped ends
were cut and inserted into surgical needles, the needles were swaged,
and the pull out forces were measured. The results are set forth
in Table II.
TABLE II ______________________________________ Pull-out forces
for Dacron .RTM. polyester 1-0 braided sutures ultrasonically cleaned
in toluene for 20 minutes. Tipping Agent Pull-Out Force kg ______________________________________
30. Silastic/Hexane 1.0-1.8 31. Paraffin/Hexane 1.0-1.6 32. Arrochem
1.3-1.8 33. Mariotte Mixture 1.8-2.5 ______________________________________
From the foregoing it would appear that ultrasonic washing in toluene
for 20 minutes prior to tipping with a conventional agent might
lead to acceptable results. Unfortunately, however, toluene is an
undesirable material due to its toxicity and the harsh effects on
the suture material.
Samples were selected for testing of (i) size O braided synthetic
absorbable sutures made from 90% glycolide, 10% lactide coated with
a glycolide/lactide/polyethylene oxide mixture, and filled with
glycerin/calcium lactate; and (ii) braided nylon (non-bioabsorbable)
sutures coated with silicone lubricant. Selected segments of the
sutures were tipped with Loctite Selected segments of the sutures
were tipped with Loctite Adhesive 18014 which was allowed to fully
polymerize. The suture segments were cut to create tipped ends which
were then inserted into a drilled hole in the barrel end of surgical
needles. The needles were then swaged by a) double hit swaging,
b) split-ring, and c) clover leaf dies, and pull out forces for
each type of attachment were measured. Further information regarding
split-ring and clover leaf swaging may be found in U.S. Pat. application
Ser. Nos. 07/431303 and 07/431306 both filed Nov. 3 1989. The
test results are set forth in Tables III, IV and V below.
TABLE III __________________________________________________________________________
Cyanoacrylate-Tipped Sutures Conventional Double-Hit Swaging PRE-STERILIZATION
POST-STERILIZATION PULL-OUT FORCE PULL-OUT FORCE SUTURE SIZE SAMPLES
AVG. RANGE SAMPLES AVG. RANGE __________________________________________________________________________
1. Synthetic Absorbable* 0 n = 5 2.6 kgs. -- n = 5 2.9 kgs. -- 2.
Braided Nylon** 0 n = 10 1.8 kgs. -- n = 10 1.8 kgs. -- __________________________________________________________________________
TABLE IV __________________________________________________________________________
Cyanoacrylate-Tipped Sutures Split Ring Swaging PRE-STERILIZATION
POST-STERILIZATION PULL-OUT FORCE PULL-OUT FORCE SUTURE SIZE SAMPLES
AVG. RANGE SAMPLES AVG. RANGE __________________________________________________________________________
3. Synthetic Absorbable* 0 n = 15 3.2 kgs. 2.9-3.7 n = 8 3.1 kgs.
2.5-3.4 kgs. kgs. 4. Braided Nylon** 0 n = 11 3.3 kgs. 1.4-7.1 n
= 15 2.9 kgs. 2.4-3.2 kgs. kgs. __________________________________________________________________________
TABLE V __________________________________________________________________________
Cyanoacrylate-Tipped Sutures Clover Leaf Swaging PRE-STERILIZATION
POST-STERILIZATION PULL-OUT FORCE PULL-OUT FORCE SUTURE SIZE SAMPLES
AVG. RANGE SAMPLES AVG. RANGE __________________________________________________________________________
5. Synthetic Absorbable* 0 n = 15 3.5 kgs. 2.8-4.4 n = 15 3.3 kgs.
2.5-4.1 kgs. kgs. 6. Braided Nylon** 0 n = 15 2.9 kgs. 1.5-3.9 n
= 15 3.2 kgs. 1.9-4.1 kgs. kgs. __________________________________________________________________________
*Synthetic Absorbable Sutures (90% glycolide/10% lactide) coated
with wit a glycolide/lactide/polyethylene oxide copolymer and filled
with glycerine/calcium lactate mixture **Braided Nylon Sutures coated
with silicone lubricant.
The minimum pull out force required by the U.S. Pharmacopeia for
size 0 suture is 1.5 kg Avg/0.45 kg individual. As can be seen from
Tables III, IV, and V, the pull out forces for the cyanoacrylate
tipped sutures exceeds the minimum USP requirements.
As can be seen from a comparison of the pull-out forces tabulated
in the above examples and comparative examples, the suture tipping
method of the present invention using cyanoacrylate tipping agent
produces pull-out forces superior to those of methods using prior
known tipping agents, particularly with respect to filled sutures
and sutures coated with lubricant coatings. Remarkably, these results
are attained without washing the suture prior to cyanoacrylate tipping.
This is surprising since the prior known methods of using cyanoacrylates
typically require the surface to be bonded to be free of oils, mold
release agents, or other foreign matter in order to achieve maximum
The following description discloses the preferred apparatus for
spraying cyanoacrylate monomer onto the suture by atomization.
METHOD FOR WINDING A SUTURE
To insure consistency of the diameter at the tipped portion of
the suture, a method and apparatus have been developed for monitoring
suture ovality and adjusting winding tension to control and, if
desired, modify the suture diameter. A diagram of the system for
loading sutures on a drum is illustrated in FIG. 4.
The pay off section includes a spool 10 on which suture material
11 is stored. A friction tensioning device applies drag to the outside
of the spool to prevent the spool from freewheeling. The suture
is guided onto a capstan 12 which is electronically controlled by
means of friction clutch 13 and clutch power supply 14. The suture
11 then passes onto the drum assembly 26. Power is supplied by standard
120 volt power sources 15. When tension is applied to the suture,
the suture diameter is reduced. When the clutch is relaxed, the
diameter of suture material under tension expands. Based on dimensional
information continuously fed to the clutch control from an x-y laser
micrometer 18 the clutch applies tension to or releases the suture
in order to maintain suture diameter within selected parameters.
The x-y laser micrometer 18 continuously monitors the diameter
of the suture in the x and y directions, i.e. suture ovality, by
means of x-y heads 19 which are oriented orthogonal to each other.
The laser micrometer electronically compares the x-y measurements
with preselected minimum and maximum dimensions pertaining to the
particular type and size of suture. This information is employed
in a negative feedback control loop whereby the clutch tension is
adjusted by means of a drive motor 17 and potentiometer clutch controller
16. In the event either dimension exceeds the maximum diameter for
the suture size, the clutch tension is increased in order to decrease
the diameter of the suture. In the event either dimension is less
than the minimum suture diameter the clutch tension is relaxed until
the suture diameter is increased into the suture diameter range.
The information is processed and clutch tension adjusted within
milliseconds of the actual measurement to continuously adjust clutch
Referring more specifically to the laser micrometer, an instrument
suitable for use in the present invention is available from Zumbach
Electronics Corp., 140 Kisco Avenue, Mount Kisco, N.Y. 10549 under
the designation ODAC 19M, which is a microcomputer controlled measuring
system having x-y heads which incorporate laser scanners.
FIG. 5 illustrates a side view of the suture handling apparatus.
Suture storage spool 10 is rotatably mounted at the top of mounting
frame 20. Suture 11 is drawn off and passes through guide 21 around
capstan 12 and over and around guide roller 22. Suture 11 then passes
through a second guide member 23 through laser micrometer 18 where
the x-y measurements are made, around guide rollers 24 and 25 and
finally onto drum 26. Drum 26 is mounted onto drum mounting frame
27 and is driven to receive suture 11 and maintain tension thereon.
During winding of the suture onto drum 26 drum mounting frame 27
traverses in the plane perpendicular to FIG. 5 so that the suture
is continuously wound around the drum in a helix from one end of
the drum to the other with no two adjacent suture portions touching.
FIGS. 6 and 7 illustrate the drum assembly 26 in greater detail.
Referring to FIG. 6 the drum assembly comprises a substantially
cylindrical drum 26 having a smooth circumferential surface 31.
In order to facilitate gentle treatment of the sutures, the drum
may be made of polished stainless steel or stainless steel covered
with a silicon rubber skin. Most preferably, drum 26 is fabricated
from high density polyethylene with steel end plates. High density
polyethylene has been found to be particularly advantageous since
excess cyanoacrylate does not adhere to this material during the
tipping operation. Where the drum is constructed of high density
polyethylene it further has been found desirable to reinforce the
drum against deformation by providing a plurality of gussets or
ribs inside the drum. An end view of one appropriate rib configuration
is shown in FIG. 6A. Each rib has a thickness of about 1/4 to 3/4
inches in the direction perpendicular to the plane of FIG. 6A. The
number of ribs may vary, but two to five ribs should be appropriate,
and three ribs are preferred. Drum 26 could also be fabricated from
a solid block of high density polyethylene, but the added weight
of such a construction most likely will not be desired.
Referring again to FIG. 6 a notch 32 extends lengthwise along
the drum. When suture 11 is wound around the drum a portion of each
suture wrap will extend across the notch orthogonally to the lengthwise
orientation of the notch. The end plate 33h has central apertures
34 and an axial spindle 29 by which the drum can be mounted to fixture
27 such that the drum can be rotated to wind suture 11 thereon.
Apertures 35 and 36 are ,for mounting the suture retainer clamps
to hold the tipped sutures in place while the tipped section is
cut to remove the sutures from the drum, as described below. Peripheral
apertures 37 are for attachment of the end plates to the drum, such
as by screw mounting, and aperture 38 is provided to receive a positioning
pin on the tipping apparatus to hold the drum in the correct orientation
during tipping. Of course, drums of different circumference can
be made in order to provide tipped sutures of different lengths.
By way of example only, drums having a circumference of thirty six,
thirty, twenty four and eighteen inches are contemplated. The cylindrical
construction of the drum has the added advantage of being conducive
to providing multiple longitudinal notches on drums of different
circumference in order to be able to tip a variety of different
length sutures in a single tipping operation. FIGS. 6B and 6C show
end elevational views of drums 26B and 26C having 2 and 3 notches,
32 respectively. It is contemplated that drums having the following
general dimensions (inches) could be provided.
______________________________________ Tipped Drum Circumference
Number of Notches Suture Lengths ______________________________________
15 3 5 16 2 8 24 2 12 ______________________________________
SPRAY TIPPING APPARATUS
The present invention contemplates tipping a suture by passing
the portion of the suture to be tipped through a mist or cloud of
rapidly curing material, such as the cyanoacrylate monomer described
above. The cyanoacrylate monomer is absorbed into the suture braid
matrix and usually cures almost immediately. Misting of the cyanoacrylate
monomer is achieved by passing it through an atomization nozzle
which atomizes the liquid monomer by means of sonic/ultrasonic vibration.
The tipping process is described more fully as follows.
After the suture 11 has been wound on drum 26 the drum may be
transferred to an apparatus 100 for tipping the suture. Such an
apparatus is illustrated in FIGS. 14 15 and 16 which are now
referred to. Drum assembly 26 with suture 11 wound thereon is mounted
onto drum mounting carriage 110 in the loading chamber 101 of the
suture tipping apparatus 100. Drum mounting carriage 110 has twin
uprights 111 each upright having a drum support plate 112 with
notches 112a for receiving spindles 29 of the drum. Mounting carriage
110 also has a base 113 with a lower member 114 for slidably engaging
rail 120 which extends longitudinally from the loading chamber 101
to the processing chamber 102. The loading chamber 101 may be accessed
by means of cover panel 103 which can be pivoted
upward to open the loading chamber 101. The tipping apparatus further
includes a control panel 130 window 104 sonic control unit 140
liquid storage and transmission system 150 metering control system
170 exhaust port 190 (FIG. 16) for removing vapors of tipping agent
and solvents, and a spray head assembly 160. The liquid storage
system 150 includes solvent reservoir 213 and tipping solution reservoir
212 and associated transmission lines as discussed below with reference
to FIG. 20. A plenum member 105 connected to a source of vacuum
extends longitudinally within processing chamber 102 to a point
below the spray head assembly 160. Plenum 105 is supported by plenum
mount 106 which is braced by gusset 106a. Long and short manifolds
107 and 108 respectively, are below base 109. At the top of the
unit 100 the sonic control unit 140 is a sonic/ultrasonic frequency
signal generator. The signal is sent to the atomizer nozzle 161
of spray head assembly 160 described below. Atomizer nozzle 161
is the outlet for the tipping solution which creates a fine mist
for spraying the suture. The electric signal from sonic control
unit is transmitted by conductive wire to piezoelectric elements
in the atomizer nozzle. A fluid passing through the nozzle is thereby
atomized into a fine mist.
A device suitable for use as the sonic control unit 140 in the
present invention is manufactured by Sono-Tek Corporation of 313
Main Mall, Poughkeepsie, N. Y..
The advantage to using sonic/ultrasonic atomization as opposed
to pressurized spray is that lower flow velocities may be used.
This eliminates bounceback of the sprayed material from the workpiece,
which is a problem
With pressure spraying. Another advantage of sonic/ultrasonic atomization
over pressure atomization is that the outlet orifice diameter of
the sonic/ultrasonic atomizer nozzle can be relatively wide while
still providing a suitable mist of tipping agent. This helps prevent
clogging of the orifice.
Yet another advantage is that the atomization creates a cloud or
mist which, when the suture is passed through, coats and saturates
all sides of the suture, not just the side of the suture facing
the outlet orifice of the atomizer. Thus, the application of tipping
agent is not limited by line of sight impingement of tipping agent
onto the suture, as would be the case with simple spray application.
Referring now to FIGS. 17 and 18 the spray head assembly 160 includes
spray nozzle 161 which comprises a downwardly projecting member
161a having an internal bore 161h terminating in orifice outlet
161g. The cyanoacrylate tipping agent passes through said bore and
is atomized to a fine mist 164 upon exiting the nozzle. Atomization
is achieved by means of piezoelectric elements 161b and 161c which
are electrically connected via wires 161d and 161e respectively
to the Sono-Tek signal generating unit 140. The signals from the
unit 140 may be varied in frequency to adjust the fineness of the
mist. O-rings 161f provide a seal for the atomization nozzle 161.
Blocks 162 have an internal chamber for an inert gas such as nitrogen,
which is fed in through gas line 163. The gas exits via apertures
162b in the bottom of the blocks 62.
Plenum member 105 has an aperture 105a positioned below the atomizer
nozzle 161 so as to catch any excess spray. The aperture also permits
the suture to be surrounded by the mist so that the entire suture,
including the underside of the suture, is uniformly coated with
the cyanoacrylate monomer.
FIG. 20 is a schematic flow chart of the tipping system. Gas supply
219 is a source of inert gas, preferably nitrogen. Optionally, a
source of compressed air may be provided with air being fed to the
ports between tipping cycles, i.e. when the instrument is not being
used. Nitrogen is sent to five port manifold 201 where it is distributed
by regulators 210 at each port to the various parts of the system.
Line 201a is distributed through 3-way valve 204 to spray ring 217.
Optional switch 224 activates the optional supply of air to the
ports when the tipping apparatus is inactive. Line 201b is distributed
through 2-way valve 207 and two 3-port flow through 206 to the ultrasonic
atomization nozzle 160 for blowing through the orifice 161g in a
clearing procedure. Line 201c is distributed to the solvent reservoir
213 for pressurization.
Line 213a from the solvent reservoir carries solvent such as acetone,
methylethylketone, or preferably 111-trichloroethane. The solvent
is used to flush residual cyanoacrylate tipping agent from the system.
Line 201d carries nitrogen through 3-way valve 204 to the inert
gas chamber 162. Line 201e carries nitrogen through metering system
170 and regulator 210 to pressurize the tipping agent storage bottle
212. The tipping agent is carried via line 212e through 3-port flow
through 206 to the atomizing nozzle 160 where it is misted and sprayed
onto a suture.
Pressurized air is sent to 2-port manifold 202 and carried via
line 202a through regulator 210 and 3-way valve 204 and 4-way valve
205 to power the carriage drive 214 from moving the drum mounting
carriage 10. Compressed air is also sent via line 202b through a
regulator 210 to a mechanism 215 for opening and closing cover panel
The tipping procedure is as follows. A drum assembly 26 with suture
11 wound thereon is placed onto the drum mounting carriage in the
loading chamber 101 of the apparatus (See FIG. 14). The cover panel
103 is closed and the tipping sequence is initiated on the control
panel 130. Compressed air powers the carriage drive 214 to move
the carriage 110 and drum assembly into the processing chamber 102.
As drum 26 enters chamber 102 plenum member 105 becomes disposed
in notch 32 beneath the suture. As the drum assembly 26 moves under
the spray head assembly 160 pressurized nitrogen at 2 psi enters
the tipping solution supply to bottle 212 and moves the tipping
agent to the nozzle 161 where it is atomized by sonic or ultrasonic
frequency generated by the Sono-Tek unit 140. Generally a frequency
of about 60 cycles is preferred although other frequencies may be
selected. The tipping agent is atomized to create a cloud or mist
164 (See FIGS. 17 and 18) which envelopes the sutures as they pass
underneath during the traverse of drum 26 into chamber 26. Only
those portions of the suture traversing the notch 32 are coated
with tipping agent. As the sutures sequentially pass through the
mist of tipping agent they are saturated with the agent which begins
to cure in a very short period of time, typically in less
than a second. The cyanoacrylate cures by polymerization catalyzed
by ambient moisture. While the tipping agent is being sprayed nitrogen
is blown through apertures 162b of inert gas chambers 162 to create
a "curtain" of nitrogen gas which blows excess tipping
agent from the suture 11 into plenum 105 to be drawn off under vacuum.
On the return pass of drum 26 from chamber 102 to chamber 101 the
suture again passes underneath the nozzle and, optionally, an additional
tipping application can be made during this pass. Alternatively,
several passes back and forth underneath the nozzle can be made
to apply tipping agent several times. When the procedure is completed,
the drum support carriage returns to the loading chamber 101 and
solvent from reservoir 213 is flushed through the system to clear
out residual tipping agent. Thereafter, nitrogen is flushed through
the atomizing head to clear out any residual solvent.
The tipping agent is preferably a solution of ethylcyanoacrylate
monomer in methylethylketone (MEK). Approximately 250 milliliters
of MEK is added to 8 ounces of ethylcyanoacrylate to adjust the
viscosity of the tipping agent to a range of from about 2 to 3 centipoise.
Methylene chloride is also an acceptable solvent.
Alternatively various other materials can be added to the tipping
solution. For example, an bioabsorbable copolymer of glycolide and
lactide may be dissolved in the tipping solution to form a biodegradable
coating on the suture braids. If such an additive is employed the
amount of MEK may have to be adjusted to keep the viscosity of the
tipping solution within a range of about 2 to 3 centipoise. Too
high a viscosity makes atomization of the tipping agent more difficult,
and inhibits wicking or absorption of the tipping agent into the
filaments of the braided suture. Referring to FIG. 19 the tipped
portion 11a of suture 11 is usually fully polymerized and dried
in about 20 to 30 seconds.
CUTTING THE TIPPED SUTURES FROM THE DRUM
After the tipping solution has polymerized, the tipped suture may
be removed from the drum by cutting the tipped suture, such as with
a scissors or by passing a razor or knife blade across the tipped
portion to create suture segments having two tipped ends suitable
for use in conjunction with a surgical needle as explained above
with reference to FIGS. 1 to 3.
In order to facilitate controlled cutting and removal of the tipped
sutures from the drum, removable drum clamps are provided to be
mounted onto the drum after tipping is complete.
A drum clamp 40 is illustrated in side view in FIG. 7. As explained
below, suture clamp 40 is mounted to drum 26 after the suture 11
has been tipped in order to retain the suture in place during removal
of the suture from the drum. Suture clamp 40 includes a main support
41 which is a U-shaped elongated member having mounting apertures
41a, as illustrated in FIG. 8. Referring again to FIG. 7 suture
clamp 40 also includes dowel arm support 42 as illustrated in perspective
view in FIG. 9. Dowel arm support 42 has dowel apertures 42a for
receiving dowels 48 which provide means for mounting the dowel support
arm to the main support 41. At least one aperture 42b on the dowel
arm support accepts button screw 49afor mounting dowel arm 43 to
dowel arm support 42a.
Referring additionally to FIG. 10 dowel arm 43 includes an elongated
aperture 43a through which button screw 49aextends for mounting
to aperture 42b on the dowel arm support. Aperture 43b retains dowel
47 for mounting into aperture 35 of drum 26 as will be explained
Suture clamp 40 further includes a rocker clamp support 44 shown
in FIGS. 7 and 11 which includes a knurled portion 44a , an aperture
44bfor accepting a button screw 49bfor mounting a rocker clamp 45
an aperture 44cfor receiving a dowel 48 for mounting to main support
41 and another aperture (not shown in FIG. 11) for receiving a
button screw 49cfor mounting rocker spring 46 to the rocker clamp
support (See FIG. 7).
Referring now to FIG. 12 rocker clamp 45 includes an elongated
aperture 45afor receiving button screw 49bfor mounting the rocker
clamp to rocker clamp support 44. The downwardly extending leg portion
of rocker clamp 45 includes a hook 45b for mounting into an elongated
aperture 36 in the drum, in a manner to be described below.
Referring to FIGS. 7 and 13 a rocker spring 46 mounts to the underside
of rocker clamp support 44 by means of button screw 49cwhich extends
through aperture 46a and into a receiving aperture in the rocker
clamp support 44.
The undersurface of the suture clamp 44 comprises a layer of soft
resilient material 50 for contacting the suture and holding the
suture to the surface of the drum 30. The preferred material for
layer 50 is a silicone rubber material available from CHR Industries,
New Haven, Conn., under the designation COHRlastic 9275. The material
is preferably of low modulus (soft). The thickness of the foam can
range from about 30 to 500 mils and is preferably about 100 to 150
In use, after suture material 11 is wound onto drum 26 on winding
apparatus 20 and the sutures have been tipped, such as by tipping
apparatus 100 a pair of suture retaining clamps 40 are mounted
to the drum on either side of notch 32 extending longitudinally
parallel thereto, as illustrated in FIG. 21. The clamps are mounted
in opposite orientation to one another, and are mounted by engaging
dowel 47 into aperture 35 of drum 26 (see FIGS. 6 and 7a), and thereafter
engaging rocker clamp hook 45b in elongated slot or aperture 36
on the drum. Hook 46b is biased by spring 46 into engagement with
elongated slot 36. With clamps 40 mounted on either side of notch
32 the tipped suture segment can be cut by knife 200 down the longitudinal
length of notch 32. Because clamps 40 retain each end of the cut
suture against the drum adjacent to the notch, the sutures do not
fall uncontrolled away from the drum. After the suture has been
cut, knurled portion 44ais pressed to overcome spring 46 and release
hook 45b from slot 36 thereby releasing the cut sutures from the
drum in a controlled manner.
It is also contemplated that clamps 40 could be mounted onto drum
26 prior to tipping and remain in place during tipping of the sutures
and removal of the tipped sutures from the drum.