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 suture having an expandable tip region
to connect 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 which comprises:
a) providing a surgical needle possessing a shank end of reduced
cross-section and a suture possessing an expandable tip region;
b) placing a shrinkable tubing around the reduced diameter shank
end of the needle and the expandable tip region of the suture;
c) shrinking the tubing; and,
d) expanding the tip region of the suture,
the shrinkage of the tubing and the expansion of the tip of the
suture causing engagement of the needle and the suture and providing
the combined surgical needle-suture device.
2. The method of claim 1 providing an ordinarily non-detachable
combined surgical needle-suture device.
3. The method of claim 1 providing a detachable combined surgical
needle-suture device.
4. The method of claim 3 wherein the shrinkable characteristics
of the tubing and the expansion characteristics of the suture tip
are such as to provide an average pull-out force falling within
the following range for the suture size indicated:
5. The method of claim 1 wherein the shrinkable tubing is fabricated
from a shrinkable metal or a shrinkable plastic.
6. The method of claim 1 wherein the shrinkable tubing is fabricated
from a shrinkable polyvinylidene fluoride plastic.
7. The method of claim 1 wherein the suture is made of a synthetic
polymer which loses substantially all of its orientation and/or
crystallinity at a temperature close to, but not as high as, its
melting point.
8. The method of claim 7 wherein the suture is a monofilament or
braided suture fabricated from a material selected from the group
consisting of nylon, polypropylene, polyethylene terephthalate,
lactide homopolymer, glycolide homopolymer, lactide copolymer and
glycolide copolymer.
9. The method of claim 1 wherein shrinking of the tubing is achieved
by application of heat to the tubing.
10. The method of claim 1 wherein expansion of the suture tip is
achieved by application of heat to the suture tip.
11. The method of claim 1 wherein the step of shrinking the tubing
further comprises applying energy to the tubing to shrink the tubing
into engagement with the needle shank end and thereafter applying
energy to the tubing to shrink the tubing into engagement with the
expandable tip region of the suture.
12. The method of claim 1 wherein shrinking of the tubing and expanding
of the suture tip are carried out simultaneously or sequentially.
13. A combined surgical needle-suture device which comprises:
a) a surgical needle possessing a shank of reduced cross-section;
b) a suture possessing an expandable tip region; and,
c) a shrinkable tubing around the reduced diameter shank end of
the needle and the expandable tip region of the suture,
the tubing being shrunk around the reduced diameter shank end of
the needle and the expanded tip region of the suture to provide
engagement of the needle and suture.
14. The combined surgical needle-suture device of claim 13 which
is an ordinarily non-detachable combined surgical needle-suture
device.
15. The combined surgical needle-suture device of claim 13 which
is a detachable combined surgical needle-suture device.
16. The combined surgical needle-suture device of claim 15 wherein
the shrinkable characteristics of the tubing and the expansion characteristics
of the suture tip are such as to provide an average pull-out force
falling within the following range for the suture size indicated:
17. The combined surgical needle-suture device of claim 13 wherein
the suture is fabricated from a fiber-forming material selected
from the group consisting of collagen, silk, cotton, linen, nylon,
polypropylene, polyethylene terephthalate, lactide homopolymer,
lactide copolymer, glycolide homopolymer and glycolide copolymer.
18. The combined surgical needle-suture device of claim 13 wherein
the shrinkable tubing is a memory metal or shrinkable plastic.
19. The combined surgical needle-suture device of claim 13 wherein
the shrinkable tubing is a shrinkable polyvinylidene fluoride material.
20. The combined surgical needle-suture device of claim 13 in which
the shank end is provided with a texturized surface to faciliatate
gripping by said shrinkable tubing.
21. The combined surgical needle-suture device of claim 20 wherein
the shank is scored, ribbed or threaded, in whole or in part.
22. The combined surgical needle-suture device of claim 13 wherein
said shank of reduced cross-section forms a shoulder with a remainder
of said needle.
23. The combined surgical needle-suture device of claim 22 wherein
said shank of reduced cross-section is tapered to expand in a direction
away from said shoulder, such that a distal end of said shank is
of greater cross-sectional diameter than cross-sectional diameter
of said shank in a region of said shoulder.
24. The combined surgical needle-suture device of claim 22 wherein
said shank of reduced cross-section is tapered to expand in a direction
toward said shoulder, such that a distal end of said shank is of
smaller cross-sectional diameter than cross-sectional diameter of
said shank 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 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 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 Pharmacoooeia 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 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 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 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. 3981307 the contents
of which are incorporated by reference herein, a suture tip is inserted
into the recess formed in the blunt end of the needle and the needle
is thereafter heated to expand the suture tip within the recess
into tight engagement with the recess walls. Sutures of synthetic
polymers attached in this manner are removable from the needle recess
by application of a straight pulling force of less than about 30
ounces.
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 which comprises:
a) providing a surgical needle possessing a shank end of reduced
cross-section and a suture possessing an expandable tip region;
b) placing a shrinkable tubing around the reduced diameter shank
end of the needle and the expandable tip region of the suture;
c) shrinking the tubing; and,
d) expanding the tip region of the suture,
the shrinkage of the tubing and the expansion of the tip of the
suture causing engagement of the needle and the suture and resulting
in the combined surgical needle-suture device.
The present invention also provides a needle-suture combination
in which the needle and suture are joined by a shrinkable tubing
and expandable suture tip. The physical and chemical characteristics
of the shrinkable tubing material, the relative diameters of the
tubing, the needle shank and the suture, the expansion characteristics
of the suture tip and the amount of energy applied to the tubing
and suture tip can 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.
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 needle possessing a
shank of reduced diameter and a suture possessing an expandable
tip with a shrinkable tubing positioned around the needle shank
and the 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 and expansion
of the suture tip to effect engagement of the needle suture; and,
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 can be used to effect standard or
detachable needle attachment as described in more detail below.
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 remainder of the needle
14 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 may 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). Shank end 12 is
placed within tubing 20 as shown in FIG. 1.
To be suitable herein, suture 30 must be capable of expansion at
its tip region 31. Suitable sutures include those disclosed in U.S.
Pat. No. 3981307 referred to suora, namely, sutures made from
a normally crystalline, oriented synthetic polymer which becomes
substantially disoriented and amorphous and is expandable at elevated
temperature. By applying heat or other suitable energy to the tip
region of a suture of this type, the suture will expand in this
region to make contact with the shrinkable tubing, the latter shrinking
under the influence of heat or other energy source as hereinafter
described to increase the compressive force between the suture tip
and the tubing.
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.
Suture 30 is positioned within shrinkable tubing 20 with expandable
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. The expandable
tip region 31 of suture 30 i.e., the region inserted into tubing
20 can be of reduced cross-section relative to the remaining portion
32 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 may be desirable
to prevent brooming of the suture, particularly for multifilament
braided sutures, by rigidifying the end of the suture thus facilitating
its handling during the attachment process. 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 the expandable
tip region of suture 30 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 the expandable tip region of
suture 30 thereby minimizing the importance of suture tipping.
After shrinkable tubing 20 is placed around shank end 12 of needle
10 and expandable tip region 31 of suture 30 energy is applied
to tubing 20 and underlying tip region 31 which causes tubing 20
to shrink and tip 31 to expand. The shrinkage of tubing 20 brings
its inner surface into engagement with shank end 12 and suture tip
31 thereby securing suture 30 to needle 10. Expansion of tip 31
brings its surface into compressive engagement with shrinking tubing
20 the two actions, i.e., expansion and shrinkage, combining to
provide engagement of the tubing and the suture.
The amount of energy applied to the tubing to effect the desired
attachment, i.e., shrinkage, 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 can be brought into engagement with shank end 12 of needle
10 and tip 31 of suture 30 either simultaneously or sequentially,
by heating tubing 20 to a temperature above 175.degree. C. Tubing
20 can 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 31. It is preferred that
the attachment conditions be controlled such that the tubing remains
secured to the needle once the suture is detached.
One suitable procedure for accomplishing expansion of expandable
tip region 31 is to raise the temperature of this region to a level
which is below the melting point of the suture material but at which
substantially all of the orientation and/or crystallinity of the
material disappears. Appropriate temperatures for this change will
vary with the nature of the material but a suitable temperature
for a particular material can be readily determined by slowly raising
the temperature of a sample of the material while observing changes
in its dimensions and birefringence in a polarizing microscope.
The sutures suitable for needle attachment by the method of the
present invention include monofilament and braided sutures. As previously
stated, the sutures can be made of any synthetic polymer which is
known to lose substantially all of its orientation and/or crystallinity
at a temperature close to, but not as high as, its melting point.
Typical synthetic polymers of this type include nylon, polypropylene,
and polyesters, such as polyethylene terephthalate, and homopolymers
and copolymers of lactide and glycolide with each other and with
other monomers.
The expansion of suture tip 31 and shrinkage of tubing 20 can be
effected simultaneously, e.g., by application of heat or other appropriate
energy which is sufficient to accomplish both actions at the same
time, or in sequence, e.g., shrinkage of tubing 20 can be achieved
by heat energy, radiation, microwave energy, etc., followed by expansion
of tip 31 accomplished by application of heat or some other type
of energy thereto, and vice versa.
The expansion characteristics of suture tip 31 and the shrinking
characteristics of tubing 20 can be selected so that in combination,
the expanded suture tip and shrunken tubing provide a gripping force
upon reduced shank 12 of needle 10 and suture tip 31 which effects
standard, i.e., ordinarily non-detachable, attachment of the needle
and suture. Alternatively, such characteristics can be selected
so as to provide a gripping force upon the needle shank and suture
tip which, to effect needle separation or detachment, can be overcome
by an average pull-out force falling within the following range
for the suture size indicated:
______________________________________ 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 ______________________________________
As shown in FIGS. 1-2 shrinkable tubing 20 is simultaneously placed
around both suture tip 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 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 to simultaneously or sequentially shrink tubing 20 and expand
suture tip 31 as previously described.
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 can be
removed from a needle and the needle attached to a fresh suture
as may be the case where the suture and/or attachment properties
of the initial suture-needle combination are outside specifications.
In many instances, the suture can 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.
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