Surgical needle abstract
A combined surgical needle-suture device of controlled suture release
characteristics and a method for manufacturing the device employ
a shrinkable tubing to connect the needle to a suture possessing
a lubricated tip.
Surgical needle claims
What is claimed is:
1. A method for attaching a surgical needle to a suture to provide
a combined surgical needle-suture device exhibiting a reduced average
level of pull-out force for a suture of given size which comprises:
a) providing a surgical needle possessing a shank end of reduced
cross-section;
b) coating a suture region with a release lubricant;
c) placing a heat shrinkable polymeric tubing around the reduced
diameter shank end of the needle and the lubricated tip region of
the suture;
d) applying energy to the shrinkable tubing to bring the tubing
into engagement with the shank end of the needle and the lubricated
tip region of the suture thereby providing the combined surgical
needle-suture device,
the average level of pull-out force required to achieve separation
of the needle and suture being significantly less than that required
for a similar combined surgical needle-suture device lacking lubricant
on the surface of the tip region of the suture.
2. The method of claim 1 wherein the average level of pull-out
force required to achieve separation of the needle and suture is
within the following range for the stated size of suture:
3. The method of claim 1 wherein the suture is a monofilament suture.
4. The method of claim 1 wherein the suture is a multifilament
suture.
5. The method of claim 1 wherein the suture is fabricated from
an absorbable or non-absorbable material.
6. The method of claim 1 wherein the shrinkable tubing is fabricated
from a memory metal or a shrinkable plastic.
7. The method of claim 1 wherein the shrinkable tubing is fabricated
from a polyvinylidene fluoride polymer.
8. A combined surgical needle-suture device which comprises:
a) a surgical needle possessing a shank end of reduced cross-section;
b) a suture possessing a tip region with a lubricant on at least
a portion of its surface; and
c) a shrinkable tubing around the shank end of the needle and the
tip region of the suture,
the tubing being shrunk around the shank end of the needle and
the tip region of the suture to provide the combined surgical needle-suture
device, the average level of pull-out force required to achieve
separation of the needle and suture being significantly less than
that required for a similar combined surgical needle-suture device
lacking lubricant on the surface of the tip region of the suture.
9. The combined surgical needle-suture device of claim 8 wherein
the average level of pull-out force required to achieve separation
of the needle and suture is within the following range for the stated
size of suture:
10. The combined surgical needle-suture device of claim 8 wherein
the suture is a monofilament suture.
11. The combined surgical needle-suture device of claim 8 wherein
the suture is a multifilament suture.
12. The combined surgical needle-suture device of claim 11 wherein
said multifilament suture is tipped with a tipping agent.
13. The Combined surgical needle-suture device of claim 12 wherein
said tipping agent is cyanoacrylate.
14. The combined surgical needle-suture device of claim 8 wherein
said shank end is provided with a texturized surface to facilitate
gripping by said shrinkable tubing.
15. The combined surgical needle-suture device of claim 14 wherein
said shank end is scored, ribbed or threaded, in whole or in part.
16. The combined surgical needle-suture device of claim 8 wherein
said shank end of reduced cross-section forms a shoulder with a
remainder of said needle.
17. The combined surgical needle-suture device of claim 16 wherein
said shank end of reduced cross-section is tapered to expand in
a direction away from said shoulder, such that a distal end of said
shank end is of greater cross-sectional diameter than cross-sectional
diameter of said shank end in a region of said shoulder.
18. The combined surgical needle-suture device of claim 16 wherein
said shank end of reduced cross-section is tapered to expand in
a direction toward said shoulder, such that a distal end of said
shank end is of smaller cross-sectional diameter than cross-sectional
diameter of said shank end in a region of said shoulder.
19. The combined surgical needle-suture device of claim 8 wherein
the suture is fabricated from an absorbable material.
20. The combined surgical needle-suture device of claim 8 wherein
the shrinkable tubing is fabricated from a polyvinylidene fluoride
polymer.
21. The combined surgical needle-suture device of claim 8 wherein
the suture is fabricated from a non-absorbable material.
22. A combined surgical needle-suture device which comprises:
a) a surgical needle possessing a shank end of reduced cross-section;
b) a suture possessing a tip region with a lubricant on at least
a portion of its surface; and
c) a heat shrinkable polymeric tubing around the shank end of the
needle and the tip region of the suture;
the tubing being shrunk around the shank end of the needle and
the tip region of the suture to provide the combined surgical needle-suture
device;
the average level pull-out force required to achieve separation
of the needle and suture being significantly less than that required
for a similar combined surgical needle-suture device lacking lubricant
on the surface of the tip region of the sutures;
wherein the suture is a multifilament suture,
said multifilament suture tipped with a tipping agent, and
wherein said tipping agent is cyanoacrylate.
23. A combined surgical needle-suture device which comprises:
a) a surgical needle possessing a shank end of reduced cross-section;
b) a suture possessing a tip region with a lubricant on at least
a portion of its surface; and
a heat shrinkable polymeric tubing around the shank end of the
needle and the tip region of the suture,
the tubing being shrunk around the shank end of the needle and
the tip region of the suture to provide the combined surgical needle-suture
device;
the average level pull-out force required to achieve separation
of the needle and suture being significantly less than that required
for a similar combined surgical needle-suture device lacking lubricant
on the surface of the tip region of the suture;
wherein the suture is a multifilament suture,
said multifilament suture coated with a suture coating along substantially
the entire length thereof, said tip region being covered with a
tipping agent, and
wherein said tipping agent is cyanoacrylate.
Surgical needle description
BACKGROUND OF THE INVENTION
The present invention relates to a method for attaching a surgical
needle to a suture to provide a combined surgical needle-suture
device possessing controlled suture release characteristics and,
more particularly, to such a method in which a shrinkable tubing,
rather than swaging or crimping, is employed to secure the needle
to the suture.
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 acids.
Needle-suture combinations fall into two general classes: standard
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).
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. 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
application.
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 from 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 relates 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, isotactic 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 stiff suture, e.g., monofilament
stainless steel.
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 cross-section as compared to the remainder of
the needle.
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), 2302886 2240330 1981651 (needle
and tubing screw threaded), 1960117 and 1591021.
Numerous disadvantages exist with methods used heretofore to effect
needle-suture attachment For example, those methods which involve
the formation and use of an axial bore in the shank end of the needle
require the use of expensive hole forming equipment. Moreover, it
is difficult to maintain the bore concentric with the center-line
of the needle and to control the depth (and diameter) of the bore
when drilling the needle shank, whether sing conventional drilling
equipment or laser drilling. Another disadvantage is the possibility
that foreign substances may inadvertently or uncontrollably be introduced
into the needle bore, e.g., oil used during drilling or lubricant,
such as silicone, from the needle coating process. Safeguards employed
in an attempt to prevent the introduction of such foreign materials,
e.g., water blocking during needle siliconization, are inconvenient
adding time, effort and cost to the needle production process.
Attachment processes which employ bored needle shanks also limit
the range of materials from which needles may be fabricated in a
cost effective fashion. For example, it is exceedingly difficult
to drill Series 300 stainless steel (laser drilling is required)
and, once drilled, it is difficult to swage Series 300 stainless
steel in a consistent and reliable manner. For this reason, Series
300 stainless steel is not employed for the vast majority of needled
suture products despite its advantageous combination of strength
and ductility characteristics as compared to conventionally employed
Series 400 stainless steel.
Additional disadvantages associated with needle-suture attachment
methods which employ bored needle shanks include the weakness imparted
to the bored section of the needle, particularly after swaging,
and the attendant increased possibility that the needle will fracture
in this region. It is also difficult to provide a specialized surface
finish to the needle shank to assist in needle attachment, e.g.,
a texturized surface and/or a tapered bore. Swaging equipment used
in such needle-suture attachment methods is also maintenance intensive.
Needle-suture attachment methods which have employed tubings heretofore
also exhibit numerous disadvantages. Methods which employ metal
tubings greatly diminish the flexibility of the needle-suture combination
in the attachment region. Such diminished flexibility has a deleterious
effect in many surgical procedures. Swaging of the tubing to the
needle and the suture is also undesirable in that swaging is time-consuming,
maintenance intensive, and subject to variability in attachment
force.
Moreover, needle-suture attachment methods which have employed
tubings heretofore have necessarily required the use of tubing having
an inner diameter essentially equal to the outer diameters of the
needle shank and suture tip to be attached. Too large a difference
between the aforesaid inner and outer diameters inhibits the attachment
process, and prevents a tight, secure interface between needle (and/or
suture) and tubing. The limited tolerance between the tubing inner
diameter and the needle shank/suture outer diameters in such methods
make these dimensions critical, thereby making the attachment process
more difficult and time-consuming, and increasing the likelihood
of attachment failure and/or rejected materials.
Commonly assigned, copending U.S. patent application Ser. No. 413240
filed Sep. 27 1989 of which the present application is a continuation-in-part,
describes and claims a combined surgical needle-suture device and
surgical needle-suture attachment method which overcomes the aforementioned
drawbacks of the previously known needle-suture combinations and
needle-suture attachment methods. In accordance with said application,
a combined surgical needle-suture device is provided in which a
surgical needle having a shank of reduced cross-section is attached
to a suture through a shrinkable tubing, or microferrule, which
is fitted about the needle shank and a portion of the suture. Application
of energy to the shrinkable tubing brings the tubing into engagement
with both the needle shank and the suture. The physical and chemical
characteristics of the shrinkable tubing material, the relative
diameters of the tubing, the needle shank and the suture, and the
amount of energy applied to the tubing may be controlled to provide
a needle-suture combination having a desired pull-out force. It
is thus possible to produce standard needle-suture combinations
and removable needle-suture combinations using a single attachment
process and a common inventory of materials.
Minimum average pull-out forces for various sizes of combined surgical
needle-suture deices are set forth in the United States Pharmacopoeia
and are as follows:
______________________________________ Average Pull-Out Suture
Size Force/Ounces ______________________________________ 8/0 2.39
7/0 3.20 6/0 5.92 5/0 7.97 4/0 15.97 3/0 23.63 2/0 38.80 1/0 52.89
1 63.48 2 and larger 63.48 ______________________________________
U.S. Pat. No. 3875946 referred to supra, describes needle-suture
combinations said to exhibit suture pull-out values that are substantially
less than those given by the United States Pharmacopoeia as set
forth above. According to U.S. Pat, No. 3875946 employing the
procedure described therein, combined surgical needle-suture devices
can be obtained with the following average pull out forces:
______________________________________ Average Pull-Out Suture
Size Forces/Ounces ______________________________________ 8/0 1-2
7/0 1-3 6/0 2-5 5/0 3-7 4/0 3-15 3/0 3-23 2/0 3-26 1/0 10-26 1 10-26
2 and larger 10-26 ______________________________________
These pull-out forces are obtained by pre-stressing the suture,
i.e., by applying tension to the suture after the tip of the suture
has been inserted into an axial bore, or recess, formed in the blunt
end of the needle and the needled suture has been swaged so that
the force required to pull the suture out of the recess exceeds
the minimum limits on needle attachment set forth in the United
States Pharmacopoeia but is less than the actual tensile strength
of the suture used. As the suture is pulled from the needle during
application of the tensioning force, the force required to move
the suture relative to the swaged section decreases. When the tensioning
force required to move the end of the suture relative to the needle
recess drops to the desired pull-out value, the tension is released.
The foregoing procedure is said to permit better control of the
resulting needle-suture device in that the force required to separate
a suture of a particular size from its attached needle is uniform.
In the approach to achieving controlled needle-suture separation
described in aforementioned U.S. Pat. No. 3963031 a combined
surgical needle-suture device of the drilled recess variety has
the suture tip inserted into the recess and held in tight engagement
therewith by crimping the needle. The aforesaid patent features
a lubricant layer at the juncture between the needle and the suture,
specifically, between the inner surfaces of the crimped recess and
the outer surface of the tip of the suture. The lubricant lowers
the pull-out value of the needle-suture combination to a value which
ranges from 3-26 ounces depending on the size of the suture.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a method
for attaching a surgical needle to a suture to provide a combined
surgical needle-suture device exhibiting a reduced average level
of pull-out force for a suture of given size which comprises:
a) providing a boreless surgical needle possessing a shank end
of reduced cross-section
b) coating a suture tip region with a release lubricant;
c) placing a shrinkable tubing around the reduced diameter shank
end of the needle and the lubricated tip region of the suture;
d) applying energy to the shrinkable tubing to bring the tubing
into engagement with the end of the needle shank and the lubricated
tip region of the suture thereby providing the combined surgical
needle-suture device,
the average level of pull-out force required to achieve separation
of the needle and suture being significantly less than that required
for a similar combined surgical needle-suture device lacking lubricant
on the surface of the tip region of the suture.
In addition to the foregoing surgical needle-suture attachment
method, the present invention includes the resulting combined surgical
needle-suture device.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become more apparent from the following
detailed description taken in conjunction with the accompanying
drawings in which:
FIG. 1 is a side cross-sectional view of a surgical needle possessing
a shank end of reduced diameter and a suture possessing a tip region
having a release lubricant coating, with a shrinkable tubing positioned
around the needle shank and suture tip (prior to engagement of the
tubing with the needle and suture);
FIG. 2 is a side cross-sectional view of the needle and suture
combination of FIG. 1 following shrinking of the tubing to effect
engagement of the needle and suture;
FIG. 3 is a side view of the combined surgical needle-suture device
of FIG. 2;
FIG. 4 is a side view of an alternative embodiment of the present
invention in which the shank end of the needle is scored;
FIG. 5 is a side view of an alternative embodiment of the present
invention in which the shank end of the needle is ribbed;
FIG. 6 is a side view of an alternative embodiment of the present
invention in which the shank end of the needle is threaded;
FIG. 7 is a side view of an alternative embodiment of the present
invention in which the needle shank end is tapered to expand in
a direction away from a remainder of the needle;
FIG. 8 is a side view of an alternative embodiment of the present
invention in which the needle shank end is tapered to expand in
a direction towards the remainder of the needle; and
FIG. 9 is a side cross-sectional view of a surgical needle possessing
a shank end of reduced diameter and a suture possessing a coating
along its length and a tip region further coated with a tipping
agent and with a release lubricant, with a shrinkable tubing positioned
around the needle shank and suture tip (prior to engagement of the
tubing with the needle and suture).
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a combined surgical needle-suture
method and resulting surgical needle-suture device featuring controlled
suture release. The invention has application to any suture material
whether absorbable or non-absorbable, natural or synthetic, braided
or monofilament, and to any needle material and configuration whether
straight or curved.
Referring to FIGS. 1-3 needle 10 has a reduced cross-sectional
diameter at its shank end 12 relative to the remainder of needle
14. The diameter of shank end 12 can be reduced by any conventional
means, e.g., machining on a lathe. Typically, shank end 12 has a
diameter from b 10 to 65% smaller than the remainder 14 of needle
10 and preferably from 25 to 50% smaller. It is also possible to
provide shank end 12 with a texturized surface to facilitate gripping
by shrinkable tubing 20. For example, shank end 12 can be scored,
ribbed or threaded, in whole or in part (FIGS. 4-6 respectively).
It can also be desirable to taper shank end 12 such that its butt,
or distal, end 16 is of greater cross-sectional diameter than the
cross-sectional diameter of shank end 12 in the region of shoulder
18 or vice versa (FIGS. 7 and 8 respectively).
Tip region 31 of suture 30 possesses a layer of release lubricant
32 upon its surface. The release lubricant functions to reduce the
pull-out force required to separate needle 14 from suture 30 to
an average value which is significantly less, e.g., from about 15
to about 75% less, than that required in the absence of lubricant
In general, this reduced average pull-out force can, by selection
of the release lubricant and its manner and amount of application,
be made to fall within the following range of values for the size
of suture indicated:
______________________________________ Average Pull-Out Suture
Size Forces/Ounces ______________________________________ 8/0 1-2
7/0 1-3 6/0 2-5 5/0 3-7 4/0 3-15 3/0 3-23 2/0 3-26 1/0 10-26 1 10-26
2 and larger 10-26 ______________________________________
While either the surface of the suture tip region or the inner
surface of shrinkable tubing 20 which is to make contact with the
surface of suture tip region 31 can be initially coated with release
lubricant, it is within the scope of this invention to apply release
lubricant to either or both surfaces. Where release lubricant is
applied solely to the inner surface of tubing 20 eventual contact
of that surface with the surface of suture tip region 31 will result
in transfer of a portion of the release lubricant to the latter
surface. The same or different release lubricants can be used in
coating the inner surface cf the tubing and the tip of the suture
where both are coated.
As disclosed in aforementioned U.S. Pat. No. 3963031 any lubricant
which is non-toxic and capable of depositing a solid, semi-solid
or liquid layer of good lubricity can be used to lubricate suture
tip region 31 and/or to lubricate the inner surface of tubing 20.
Suitable lubricants include silicone polymers; polyhaloalkylene
polymers, particularly polytetrafluoroethylene; polyalkylene glycol
polymers such as methoxy polyethylene glycol and polypropylene glycol;
polytetramethylene glycol polymers with a molecular weight the range
of from about 2000 to about 13000; hydroxyl-terminated polyester
polymers from di-acids and glycols such as polytetramethylene idiopathy
polymer; hydroxyl-terminated polyester polymers resulting from the
polymerization of lactones such as epsilon-capralactone in the presence
of a polymethylene diol such as 14-butanediol; metallic stearates
such as aluminum stearate, calcium stearate and zinc stearate; long
chain aliphatic amides such as coconut oil amide, oleamide and stearamide;
glycerol esters of long chain fatty acids such as glycerolmono-
and distearates, glycerol mono- and dioleates, and glycerol mono-
and dilaurates; animal waxes such as spermaceti; insect waxes such
as beeswax; vegetable waxes such as carnauba wax, Japan wax and
cocoa butter; mineral waxes such as petrolatum, paraffin wax, micro-crystalline
waxes and montan wax; and polyolefins such as polyethylene dispersions
The lubricant is advantageously applied from a volatile liquid
carrier. The carrier can be a solvent for the lubricant or the lubricant
can be finely dispersed in a non-solvent liquid. Typical carriers
which can be either solvents or non-solvents depending on the nature
of the lubricant include water, hydrocarbons such as n-heptane,
benzene and toluene and halogenated hydrocarbons.
In some cases a lubricant can be used without a carrier, particularly
a lubricant which is produced in situ by proceeding from a monomeric
state to a polymeric state or from an uncured state to a cured state.
Some silicone materials are commonly sold and used without a solvent
or carrier and can serve in the uncured state as adhesives. They
can be cured in situ, however, to produce stable silicone polymer
coatings which have lubricant properties
Application of release lubricant to the surface of suture tip region
31 and/or the inner surface of shrinkable tubing 20 can be accomplished
by any of several methods, e.g., dipping, spraying, coating, etc.
The material of suture 30 can be any of the filament-forming natural
and synthetic materials heretofore employed in the fabrication of
sutures, e.g., absorbable materials such as gut, collagen, homopolymers
and copolymers of lactide and glycolide, etc., and non-absorbable
materials such as silk, nylon, polypropylene, cotton, linen and
some types of polyester.
The amount of release lubricant employed can vary within relatively
large limits and is not critical provided at least a lubricating
amount of release lubricant is present on the inner surface of shrinkable
tubing 20 and/or tip region 31 of suture 30. Specific quantities
of release lubricant for a particular combined surgical needle-suture
device and desired pull-out force can be readily determined employing
routine experimentation.
It is also known to coat or impregnate sutures with lubricant materials
such as wax or polytetrafluoroethylene in order to improve suture
handling, knot run down and knot tying characteristics. Notwithstanding
the presence of such a suture coating, the coated suture tip remains
relatively limp, and is not sufficiently stiff to be inserted into
a needle recess. Coated braid sutures are also known to experience
brooming, which further makes it difficult or impossible to position
the suture tip for needle attachment. To overcome these problems,
braided sutures typically are "tipped" with a material
which prevents brooming of the suture filaments and stiffens the
suture tip to facilitate attachment of the suture to a needle. Suture
coatings ordinarily are removed from the suture prior to tipping,
or are coated over with the tipping agent.
In accordance with the present invention, it is desirable to remove
suture coatings or to coat over the suture coatings with a tipping
agent. In order to simplify manufacture and reduce process steps,
it is desirable to eliminate the need to remove any suture coating
by providing a tipping agent that effectively coats over all types
of suture coatings. Cyanoacrylate, particularly Loctite.TM. Medical
Adhesive 18014 has been found to satisfy these requirements Indeed,
it has been found that cyanoacrylate tipping thoroughly covers the
suture coating and creates a barrier between the suture coating
and a release lubricant applied to the suture tip in accordance
with the present invention. In this manner, the release characteristics
of the needle-suture attachment in accordance with the invention
advantageously can be determined and controlled independent of the
suture coating by optimizing the type and amount of release lubricant
applied over the tipping agent.
In accordance with this aspect of the invention, as shown in FIG.
9 suture 30 which may be a braided suture, having a suture coating
34 over the entire length thereof is tipped with a tipping agent
36 preferably cyanoacrylate. Thereafter, in accordance with the
invention lubricant layer 32 is applied to a suture tip region 31
over tipping agent 36.
Suture 30 is positioned within shrinkable tubing 20 with suture
tip 31 abutting or sep a short distance from distal end 16 of shank
12. As shown in FIG. 1 suture 30 can initially be of uniform cross-section
throughout its length. Alternatively, tip region 31 of suture 30
i.e., the region inserted into tubing 20 can reduced cross-section
relative to the remainder of suture 30 e.g., by tipping the suture
tip with an adhesive or resinous tipping agent while suture 30 is
under tension. (See, e.g., Canadian Patent No. 1009532.) Reducing
the diameter of the suture tip as by resin tipping is advantageous
in preventing brooming of the suture, particularly in the case of
multifilament braided sutures, and/or to rigidify tip 31 to facilitate
handling of the suture during attachment. It is not necessary according
to the present invention, however, to reduce the diameter of tip
region 31 to efficiently attach needle 10 to suture 30. Indeed,
it may be possible or desirable to apply a tipping agent to prevent
brooming without reducing suture diameter. As shown in FIG. 1 shrinkable
tubing 20 initially has an inner diameter that is larger than the
outer diameter of suture tip region 31 thereby reducing the importance
of suture tipping.
After shrinkable tubing 20 is placed around shank end 12 of needle
10 and tip region 31 of suture 30 energy is applied to tubing 20.
In response to this energy, tubing 20 contracts or shrinks and engages
shank end 12 and suture tip region 31. The overall length of tubing
20 may also be affected by the application of energy, e.g., the
length of tubing 20 may reduce. Thus, the shrinking of tube 20 brings
the inner surface of tubing 20 into engagement with shank end 12
and suture tip region 31 thereby securing suture 30 to needle 10.
Suitable energy sources include heat (convective or conductive),
radiation, microwave energy, etc.
As shown in FIGS. 1-2 shrinkable tubing 20 is simultaneously placed
around both suture tip region 31 and shank end 12 of needle 10 in
one embodiment of the present invention. It is preferable, however,
to sequentially secure tubing 20 to needle 10 and suture tip region
31. Thus, in a preferred embodiment of the present invention, shrinkable
tubing 20 is initially secured to shank end 12 through the localized
application of energy to tubing 20 in the region surrounding shank
end 12. After tubing 20 has been brought into engagement with shank
end 12 tip 31 of suture 30 is inserted into tubing 20 and additional
energy is applied thereto. Sequential shrinkage of tubing 20 makes
it possible to vary the amount of energy used in securing tubing
20 to shank end 12 and suture tip 31 respectively, and to limit
the exposure of suture 30 to energy during the attachment process.
It may also be desirable to cool suture 30 in the region outside
tubing 20 to prevent any undesirable degradation thereof, e.g.,
with a cold air curtain.
As shown in FIG. 2 the shrinkage of tubing 20 typically compresses
suture 30 to some extent. This is particularly true where the suture
is a braided multifilament material having void spaces in its structure.
For example, tubing 20 may compress suture 30 by as much as 30 to
35% for a braided, synthetic absorbable suture and by a minimal
amount for a relatively stiff material such as a monofilament surgical
gut.
Shrinkable tubing 20 can be manufactured from any material which
shrinks, i.e., reduces in diameter, in response to the application
of energy. Suitable materials include "memory metals,"
e.g., nickel-titanium mixtures, 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 4773680),
and shrinkable plastic materials such as polyvinylidene fluoride
materials available from Raychem Corporation, Menlo Park, Calif.
under the tradename Kynar. In the case of shrinkable plastic materials,
the tubing is typically extruded such that the inner diameter is
less than the final desired inner 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
of expanded inner diameter as shown, for example, by tubing 20 in
FIG. 1. 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.
The amount of energy applied to the tubing to effect the desired
attachment, i.e., diameter reduction, depends upon the chemical
characteristics of the tubing material, the relative dimensions
of the tubing, the shank end of the needle and the suture, and the
desired pull-out force for the needle-suture combination. For example,
one polyvinylidene fluoride material available from Raychem Corporation
(TT-850) shrinks at temperatures greater than 175.degree. C., and
is adapted to recover to about 50% of its radially expanded inner
diameter. In such case, tubing 20 may be brought into engagement
with shank end 12 of needle 10 and suture tip region 31 either
simultaneously or sequentially, by heating tubing 20 to a temperature
above 175.degree. C. Tubing 20 may be heated through contact with
a hot gas stream or with heated dies, or by other heating means.
Typically, the outer diameters of shank end 12 and suture tip region
31 are greater than the fully recovered diameter of tubing 20 e.g.,
greater than 50% of the initial inner diameter of tubing 20 for
the RT-850 material, such that tubing 20 engages shank end 12 and
suture tip region 31. It is preferred that the attachment conditions
be controlled such that the tubing remains secured to the needle
once the suture is detached.
The foregoing surgical needle-suture attachment procedure has many
advantages over previous attachment methods. Machining of the needle
to provide a reduced diameter needle shank is much easier and more
controllable than drilling processes, and permits the use of needle
alloys which have previously been impractical, e.g., Series 300
stainless steel and MP35N (available from SPS Technologies). These
heretofore impractical alloys have advantageous strength and ductility
characteristics as compared to conventionally used Series 400 stainless
steels. Moreover, an unreliable, expensive and maintenance intensive
swaging process is replaced by a sterile, controllable and relatively
inexpensive energy supply. The tubing used in the present invention
may be color coded to designate suture material, standard versus
detachable attachment, etc., particularly where a plastic tubing
is employed.
The attachment method is also much more efficient from a processing
and inventory control standpoint. For example, the tubing may be
removed from a needle and the needle attached to a fresh suture,
e.g., in instances where the suture and/or attachment properties
of the initial suture-needle combination are outside specifications.
In many instances, the suture may also be recovered and reused,
thereby greatly reducing processing waste. The range of acceptable
suture diameters is greatly expanded due to the ability of the tubing
to recover or shrink to varying degrees, thereby minimizing the
likelihood that suture production will be rejected for inability
to attach several needle sizes because the shrinkable tubing is
capable of recovering or shrinking to varying degrees. This greatly
simplifies inventory considerations. Moreover, the needle-suture
combinations are atraumatic and advantageously exhibit flexibility
in the attachment region.
While the above description contains many specifics, these specifics
should not be construed as limitations on the scope of the invention,
but merely as exemplifications of preferred embodiments thereof.
Those skilled in the art will envision many other possible variations
that are within the scope and spirit of the invention as defined
by the claims appended hereto. |