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 and a bonding agent to attach the needle to
the suture.
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 predetermined
average range of separation force for a suture of given size which
comprises:
a) providing a surgical needle possessing a shank end of reduced
cross-section and a suture possessing a tip region for attachment
to the reduced diameter shank end of the needle;
b) providing a shrinkable tubing for placement around the reduced
diameter shank end of the needle and the tip region of the suture;
c) providing a bonding agent upon at least some portion of the
inner surface of the shrinkable tubing to come into contact with
the tip region of the suture and/or upon at least some portion of
the tip region of the suture;
d) placing the shrinkable tubing around the reduced diameter shank
end of the needle and the tip region of the suture; and,
e) applying energy to the shrinkable tubing to contract the tubing
and bring it into engagement with the shank end of the needle and
the tip region of the suture thereby resulting in attachment of
the needle to the suture and providing the combined surgical needle-suture
device,
the combined attachment effect of the contracted tubing and the
bonding agent being sufficient to provide a predetermined average
range of needle separation force.
2. The method of claim 1 wherein the average needle separation
force ranges from about 1 to 56 ounces.
3. The method of claim 1 wherein the average needle separation
force is within the following range for the stated size of suture:
4. The method of claim 1 wherein the bonding agent is a wax composition
having a melting a point above about 95.degree. C. and in step (e),
a sufficient amount of heat is applied to the wax composition to
cause at least the softening thereof.
5. The method of claim 1 wherein the bonding agent is a wax composition
selected from the group consisting of natural wax, fossil wax, earth
wax, petroleum wax and synthetic wax.
6. The method of claim 1 wherein the wax composition is comprised
of candelilla wax.
7. The method of claim 1 wherein the suture is a monofilament suture.
8. The method of claim 1 wherein the suture is a multifilament
suture.
9. The method of claim 1 wherein the suture is fabricated from
an absorbable or non-absorbable material.
10. The method of claim 1 wherein the shrinkable tubing is fabricated
from a memory metal or a shrinkable plastic.
11. The method of claim 1 wherein the shrinkable tubing is fabricated
from a polyvinylidene fluoride polymer.
12. A combined surgical needle-suture device exhibiting a predetermined
average range or needle separation force for a suture of given size
which comprises:
a) a surgical needle possessing shank end of reduced cross-section;
b) a suture possessing a tip region for attachment to the shank
end of the needle;
c) a constricted tubing around the reduced diameter shank end of
the needle and the tip region of the suture, the constricted tubing
exerting an attachment force against the surfaces of the reduced
diameter shank end of the needle and the tip region of the suture
with which the inner surface of the constricted tubing is in contact
without swaging or crimping; and,
d) a bonding agent upon at least some portion of the inner surface
of the constricted tubing which is in contact with the tip region
of the suture and/or upon at least some portion of the tip region
of the suture, the bonding force of the bonding agent in combination
with the attachment force of the constricted tubing providing a
predetermined average range of needle separation force.
13. The combined surgical needle-suture device of claim 12 wherein
the average needle separation force ranges from about 1 to 56 ounces.
14. The combined surgical needle-suture device of claim 12 wherein
the average needle separation force is within the following range
for the stated size of suture:
15. The combined surgical needle-suture device of claim 12 wherein
the bonding agent is a wax composition having a melting a point
above about 95.degree. C.
16. The combined surgical needle-suture device of claim 12 wherein
the bonding agent is a wax composition selected from the group consisting
of natural wax, fossil wax, earth wax, petroleum wax and synthetic
wax.
17. The combined surgical needle-suture device of claim 12 wherein
the wax composition is comprised of candelilla wax.
18. The combined surgical needle-suture device of claim 12 wherein
the suture is a monofilament suture.
19. The combined surgical needle-suture device of claim 12 wherein
the suture is a multifilament suture.
20. The combined surgical needle-suture device of claim 12 wherein
the suture is fabricated from an absorbable or non-absorbable material.
21. The combined surgical needle-suture device of claim 12 wherein
the shrinkable tubing is fabricated from a memory metal or a shrinkable
plastic.
22. The combined surgical needle-suture device of claim 12 wherein
the shrinkable tubing is fabricated from a polyvinylidene fluoride
polymer.
23. The combined surgical needle-suture device of claim 12 wherein
the shank end of the needle is provided with a texturized surface
to facilitate gripping by said tubing.
24. The combined surgical needle-suture device of claim 23 wherein
the shank end is scored, ribbed or threaded in whole or in part.
25. The combined surgical needle-suture device of claim 12 wherein
the shank end of reduced cross-section forms a shoulder with a remainder
of said needle.
26. The combined surgical needle-suture device of claim 25 wherein
the shank end is tapered in a direction toward 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.
27. The combined surgical needle-suture device of claim 25 wherein
said shank end is tapered in a direction away from 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.
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
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 nonabsorbable, 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 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 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. No. 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 valve 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), 2302986 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 using 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 silicone
from the needle silconization process. Safeguards employed in an
attempt to prevent the introduction of such foreign materials, e.g.,
water blocking during needle silconization, 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 Sept. 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 devices 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 are 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 Force/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 prestressing 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. 4127133 the contents
of which are incorporated by reference herein, a combined surgical
needle-suture device of the drilled recess variety employs a bonding
agent, specifically, a hot melt wax, to effect attachment of the
suture to the needle. The bonding agent possesses a strength sufficient
to secure the needle to the suture during surgery but which allows
the needle to be deliberately separated from the suture by a sharp
tug at the end of the surgical procedure. The bonding agent provides
pull-out values ranging from 1-56 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 predetermined average
range of needle separation force for a suture of given size which
comprises:
a) providing a surgical needle possessing a shank end of reduced
cross-section and a suture possessing a tip region for attachment
to the reduced diameter shank end of the needle;
b) providing a shrinkable tubing for placement around the reduced
diameter shank end of the needle and the tip region of the suture;
c) providing a bonding agent upon at least some portion of the
inner surface of the shrinkable tubing to come into contact with
the tip region of the suture and/or upon at least some portion of
the tip region of the suture;
d) placing the shrinkable tubing around the reduced diameter shank
end of the needle and the tip region of the suture;
e) applying energy to the shrinkable tubing to contract the tubing
and bring it into engagement with the shank end of the needle and
the tip region of the suture thereby resulting in attachment of
the needle to the suture and providing the combined surgical needle-suture
device,
the combined attachment effect of the contracted tubing and the
bonding agent being sufficient to provide a predetermined average
range of needle separation force.
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 bonding
agent-coated tip region 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 needle shank is scored;
FIG. 5 is a side view of an alternative embodiment of the present
invention in which the needle shank is ribbed;
FIG. 6 is a side view of an alternative embodiment of the present
invention in which the needle shank is threaded;
FIG. 7 is a side view of an alternative embodiment of the present
invention in which the needle shank is tapered to expand in a direction
away from a remainder of the needle; and
FIG. 8 is a side view of an alternative embodiment of the present
invention in which the needle shank is tapered to expand in a direction
towards the remainder of the needle.
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.
As used herein, the expressions "needle separation" and
"suture release" are to be regarded as functionally equivalent
since the effect of "needle separation" and "suture
release" are one and the same, i.e., the needle and suture
become detached from one another.
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., by machining on a lathe. Typically, shank end 12 has
a diameter from 10 to 65% smaller than the remaining portion 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 bonding agent 32
on at least some portion of its surface. The combined action of
tubing 20 following its contraction and bonding agent 32 functions
to provide a separation force for separation of needle 14 from suture
30 to within a predetermined average range, e.g., from about 1-56
ounces depending on suture size, as in aforementioned U.S. Pat.
No. 4127133. It is preferred that the average range of needle
separation force fall within the following range of values for the
size of suture indicated:
______________________________________ Average Needle Separation
Suture Size Force/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 ______________________________________
Either or both suture tip region 31 and inner surface of shrinkable
tubing 20 which is to make contact with suture tip region 31 can
be provided with the bonding agent, e.g., as a layer or coating
thereof on their respective surfaces. The same or different bonding
agents can be used in coating the inner surface of the tubing and
the tip of the suture where both are coated.
The bonding agents which are useful herein include those materials,
denominated "wax compositions", described in aforementioned
U.S. Pat. No. 4127133. The expression "wax compositions"
includes waxes and waxlike materials which, although not technically
true waxes, nevertheless possess many of the attributes of waxes
and are generally recognized to be useful as wax substitutes. Useful
waxes include natural wax, fossil or earth wax, petroleum wax and
synthetic wax. Natural waxes include waxes from insects (beeswax),
animals (woolwax) and plants (palm tree, candelilla, cotton and
hemp wax). Fossil and earth waxes include montan wax and certain
paraffin waxes. Petroleum waxes include rod wax, paraffin wax and
microcrystalline wax. Synthetic waxes include polyethylene wax,
ethylene copolymer wax, carbowax and halogenated hydrocarbon waxes.
A preferred wax is candelilla, a relatively hard brittle wax, having
a shore Durometer hardness value of 99-100 at 25.degree. C., a melting
point of from 68.5.degree. to 72.5.degree. C., a flash point of
241.degree. C., and paraffinic hydrocarbons of 45 percent minimum.
Candelilla and other waxes useful as bonding agents herein can
be formulated with each other or with nonwax polymers, resins, rubbers,
pigments, extenders, and the like, in order to control the melting
point, hardness, color, viscosity or bonding strength of the wax.
For example, waxes such as candelilla and/or paraffin can be formulated
with ELVAX, a wax-compatible ethylene/ vinyl acetate copolymer (a
product of E. I. duPont de Nemours & Company). ELVAX is reported
to be a general-purpose resin designed for use with paraffin and
microcrystalline waxes to provide good toughness and flexibility
at moderate melt viscosity. Blending of ELVAX with petroleum waxes
effectively improves the bonding strength of the wax (DuPont Bulletin
Pl. 14-171 "ELVAX Vinyl Resins").
The bonding agent can be applied to the inner surface of shrinkable
tubing 20 and or the surface of suture tip 31 by melt-dipping or
as a solution in a suitable carrier or solvent, e.g., petroleum
ether or other suitable hydrocarbon solvent in the case of the foregoing
waxes. Other application methods include spraying, coating and so
forth. The amount of bonding agent employed can vary over a relatively
wide range and is not critical provided the resulting bond, or attachment,
force in combination with the attachment force of tubing 20 following
shrinking of the latter provide a predetermined needle separation
force of appropriate magnitude, e.g., 1-56 ounces and preferably
1-26 ounces depending on the size of the suture. Specific quantities
of bonding agent(s) for a particular combined surgical needle-suture
device and desired pull-out force can be readily determined employing
routine experimentation.
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.
Suture 30 is positioned within shrinkable tubing 20 with suture
tip 31 abutting or separated 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 be of
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.) 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. Reducing the diameter of the suture tip,
as by tipping under tension, may be desirable to allow a suture
of larger diameter, e.g., a suture diameter equal to the diameter
of the needle to which it is to be attached, to be more efficiently
attached to the needle using the shrinkable tubing of the present
invention. 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. At the same time, this application
of heat melts wax bonding agent 32 such that on re-solidification
of the wax, the subsequent adhesive bond formed between suture tip
31 and the inner wall of constricted tubing 20 and the gripping
force of tubing 20 effect attachment of the needle and suture. 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 multi-filament 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 tubing 20 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
(RT-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. |