Suture needle abstract
A suture needle has a unique structure for reducing impalement
resistance. The suture needle is formed with a base end portion
formed at an end of the suture needle for engaging a suture thread,
a tip portion formed at another end of the suture needle for impaling
a tissue, and a tapered portion extending to the tip portion. The
tapered portion has a cross-section without a cutting edge and a
plurality of roughened regions formed in stripes extending in a
substantially axial direction of the tapered portion. The roughened
regions are provided solely on the tapered portion of the suture
needle. The surface roughness of the roughened regions on the suture
needle is about 2 .mu.m-15 .mu.m.
Suture needle claims
What is claimed is:
1. A suture needle, comprising:
a base end portion, at an end of said suture needle, for engaging
a suture thread;
a tip portion, at another end of said suture needle, for impaling
a tissue; and
a tapered portion reaching to said tip portion, said tapered portion
having a cross-section without a cutting edge and a plurality of
roughened regions formed in stripes extending in a substantially
axial direction of said tapered portion, said roughened regions
being provided solely on said tapered portion and having a surface
roughness of about 2 .mu.m-15 .mu.m.
2. The suture needle as claimed in claim 1 wherein said roughened
regions are polished to increase their smoothness.
3. The suture needle as claimed in claim 1 wherein a portion of
said tapered portion near the tip has a polished surface.
4. The suture needle as claimed in claim 1 wherein the tip portion
has a cutting edge.
5. The suture needle as claimed in claim 1 wherein a silicon coating
is applied to said tapered portion.
6. The suture needle as claimed in claim 3 wherein length, in
an axial direction of the suture needle, of said polished surface
at said portion of said tapered portion near the tip is 5% to 20%
in length, in an axial direction, of said tapered portion and a
surface roughness of said polished surface is about 0.2 .mu.m-0.5
.mu.m.
7. The suture needle as claimed in claim 4 wherein length, in
an axial direction of the suture needle, of said cutting edge at
said tip portion is 5% to 20% in length, in an axial direction,
of said tapered portion and a surface roughness of said cutting
edge is about 0.2 .mu.m-0.5 .mu.m.
Suture needle description
FIELD OF THE INVENTION
The present invention relates to a suture needle for medical use,
and more particularly, to a suture needle having reduced impalement
resistance.
BACKGROUND OF THE INVENTION
Many kinds of medical suture needles have been used in accordance
with their usage, for example, dull needles, square needles, and
round needles have representatively been utilized.
A dull needle is used for suturing lever and the like, and a tip
of the needle is dull. A square needle is generally used for suturing
hard tissue such as skin and muscle, and has a sharp tip and a tapered
portion with a shape of a polygonal pyramid, and each prescribed
edge on the tapered portion is used as a cutting edge to cut and
open a tissue.
A round needle is provided with a body with an appropriate cross-section
and a conically tapered portion on the side of a tip thereof. Although
the shape of the cross-sections of the conically tapered portion
and the body are usually round, in place of the round cross-section,
an oval which is sandwiched between two substantially parallel planes,
a cross-section enclosed by four planes, and a cross-section which
is sandwiched between two substantially parallel planes and of which
central portion is constricted may be adopted. However, the tapered
portion of a round needle is not adapted to be used as a cutting
edge which is obtained by sharpening an edge like a square needle.
After piercing a tissue with a tip, a round needle enlarges the
pierced hole with the tapered portion. Unlike a square needle, a
round needle is not provided with a cutting edge at the tapered
portion, so that the needle does not cut a tissue unnecessarily.
Therefore, a tissue at the hole closely contacts the surface of
a thread, which prevents body fluid and the like from being spilt
from the sutured portion. With this characteristics, a round needle
is mainly used for suturing blood vessels and soft tissues.
The above-mentioned round needle is manufactured in the following
manner.
At first, a linear (straight shaped) material with a prescribed
diameter is cut in a predetermined length. Then, a portion engaging
a suture thread is formed at an end of the linear material. As the
engaging portion, for instance, a spring eye, or a blind hole which
is drilled in an axial direction of the linear material is adopted.
Next, a tip and an intermediate portion of the material are ground
with a whetstone or the like to form a sharp tip and a tapered portion.
Then, rough buff polishing and another polishing with fine whetstone
or the like are performed. Then, grinding stripes are removed through
buff polishing, electrolytic polishing or the like to make mirror-finished
surface. The straight material is bent to form a prescribed shape,
and heat treatment and surface treatment are applied to complete
the round needle.
In this connection, a demand for the sharpness of a needle, that
is, the reduction of impalement resistance has been becoming considerably
strong. However, it is difficult to increase the cutting quality
of a round needle without cutting edge. In case of a square needle
such as a triangular suture needle, as described above, edges at
the pyramid-shaped tapered portion function as cutting edges to
open a tissue while the needle proceeds in the tissue, so that it
is relatively easy to reduce impalement resistance. However, in
such a case, the square needle opens tissue with the edges thereof,
therefor, cut section becomes large to cause poor sealing property
after an impalement of the needle to decrease, resulting in spilt
of body fluid. Therefore, the square needle is not suitable for
the suture of blood vessels and the like.
To solve the above-mentioned problems, in prior art, the surface
of the needle is mirror-finished to reduce the impalement resistance.
That is, as a surface treatment in the above-mentioned manufacturing
process, a finishing process through buff polishing, electrolytic
polishing, chemical polishing or the like is carried out to form
a mirror surface.
In the finishing process through buff polishing, cotton cloth,
felt, or the like with fine abrasive grain is rotated and is pressed
against the material to be ground to cause the abrasive grain to
polish and finish the material, which allows a tip and a body of
a needle to be mirror-finished.
In the finishing process through electrolytic polishing, electricity
is forced to be applied to a needle to melt the surface of the needle
through electrolysis.
In the finishing process through chemical grinding, unlike the
finishing process through electrolytic grinding, electricity is
not forced to be applied, but acid causes the surface of a needle
to be melt. In this case also, polish and finished surface becomes
mirror surface.
With the above-mentioned finishing processes, although the finished
surface looks like a smooth mirror surface with naked eyes, it is
not a mirror surface microscopically. For instance, with the buff
finishing, many rough stripes caused by abrasive grain are observed.
Further, with respect to the electrolytic grinding, microscopically,
it is confirmed that gases generated at the electrolysis adhere
to the surface to form a rough surface with shallow craters.
With the chemical grinding, besides the rough surface with craters
caused by the gases like the electrolytic polishing, further shallow
roughness is formed on the surface of a needle by easily ground
crystal grains and hardly ground crystal grains of the material
of the needle.
As described above, there are all kinds of mirror-finishing, and
whether a complete mirror surface or not is not automatically determined,
in other words, the degree of the mirror finishing varies with material
to be ground. For example, mirror-finishing for silicon wafer and
that for plate member for constructing buildings are different from
each other. In the detailed description of the invention, a mirror
surface is defined to be such a finished surface of a needle as
finished by generally used buff polishing, electrolytic polishing,
or chemical polishing.
However, even with the more microscopically smooth mirror surface
of a needle, the impalement resistance of the needle is not be reduced.
In other words, there is no difference between the mirror surfaces
formed through the buff polishing, electrolytic polishing, chemical
polishing, and more smooth mirror surface.
In another method in the prior art for decreasing the impalement
resistance, a tapered portion is coated with silicon. However, in
this case, the silicon coating is peeled off after several impalements,
thus, the effect of the silicon is significantly decreased.
To solve the above-mentioned problem, in Japanese Patent Publication
No. Heisei 5-18576 it is proposed that channels with craters are
formed on a tapered portion of a needle through chemical grinding,
and silicon is applied onto the tapered portion. With such construction,
silicon is sustained in the crater-like concave portions, and even
after the needle is repeatedly used, the increase in the impalement
resistance may be prevented.
However, in a suture needle in which silicon is sustained in the
crater-like concave portions formed by the chemical polishing, as
described above, the concave portions are very shallow as generally
called as a mirror surface, the silicon is not so effective.
Further, in another Japanese Patent Publication No. Heisei 5-60746
it is disclosed that, in order to reduce the impalement resistance,
a tapered portion near the tip of the needle is formed to be long
to decrease the taper ratio (that is, the portion is formed to be
thin and sharp).
However, when the taper ratio of the needle is decreased, such
a needle is effective to a thin tissue but is not effective to a
thick tissue as explained below.
Generally, it is known that there are two peaks of impalement resistance
of a round needle. The first peak is observed when the tip of the
needle enters a tissue, and the second peak is observed when the
end of the tapered portion (the thickest portion) enters the tissue.
In other words, the moment the tip of the needle just enters the
tissue, the first peak is observed, and after that, the resistance
is lowered once. Then, the resistance value gradually increases
as the tapered portion becomes thicker, and when the end of the
tapered portion, that is, when the thickest portion enters the tissue,
the second peak is observed.
A sharper tip of a needle causes the first peak to be decreased.
In other words, if a tissue is so thin that the tip of the tapered
portion penetrates the tissue, the sharper tip is effective. However,
when the tissue is thick in comparison to the long tapered portion,
not only the long gentle tapered portion but also a short steep
tapered portion contacts the tissue from the tip to the end of the
needle, so that work loads of both tapered portions are the same
(impalement resistance here is calculated by the following formula:
impalement resistance=the coefficient of friction.times.pressure.times.distance
that the tapered portion contacts the tissue).
As in the foregoing, the change in the taper ratio allows the pressure
to be decreased, however, the distance that the tapered portion
contacts the tissue becomes longer. Therefore, the sharper tip is
not effective. This is applied not only to a round needle but to
a needle with cutting edge only at the tip, so-called a cutting
tapered needle. That is, the above problem is applicable to all
types of needle without cutting edges at the tapered portion where
the cross-section of the needle becomes large.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above-mentioned
fact and, it is therefore an object of the present invention to
provide a suture needle in which impalement resistance is further
decreased in comparison to a conventional one.
To achieve the above object, the suture needle according to the
present invention comprising a base end portion, at an end of the
suture needle, engaging a suture thread, a tip, at another end of
the suture needle, impaling a tissue, and a tapered portion reaching
to the tip, characterized in that the tapered portion is provided
with a roughness of which stripe extends in a substantially axial
direction thereof. This stripe roughness is solely provided on the
tapered portion to improve the impalement resistance.
The stripe roughness is rougher and longer than the mirror surface
of the suture needle described above. For example, the depth of
the stripe roughness of the suture needle according to the present
invention is approximately in the range between 2 .mu.m and 15 .mu.m
while the surface roughness of the mirror surface of the suture
needle is approximately in the range between 0.2 .mu.m and 0.5 .mu.m.
This stripe roughness is formed by grinding with whetstone or the
like, and rougher surface compared with this stripe roughness is
excluded.
It is possible to mirror-finish only the tip portion of the tapered
portion, or form cutting edge to the portion, or apply silicon treatment
to the tapered portion.
Further, it is also possible that the tapered portion is not provided
with a cutting edge; the stripe roughness is formed by grinding;
the stripe roughness is more than twice as rough as that of a mirror
surface; the stripe roughness is polished to a degree that the stripe
disappears; a portion of the tapered portion near the tip of the
suture needle has mirror surface; a portion of the tapered portion
near the tip of the suture needle has a cutting edge; silicon treatment
is applied to the tapered portion; length, in an axial direction
of the suture needle, of the mirror surface at the portion of the
tapered portion near the tip of the suture needle is 5% to 20% in
length, in an axial direction, of the tapered portion; and length,
in an axial direction of the suture needle, of the cutting edge
at the portion of the tapered portion near the tip of the suture
needle is 5% to 20% in length, in an axial direction, of the tapered
portion.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be more apparent from the ensuring description
with reference to the accompanying drawings, wherein:
FIG. 1 is a perspective view showing an overall suture needle according
to the present invention;
FIG. 2 is an enlarged view of the tapered portion and the base
end portion, which are arranged in a row, of the suture needle shown
in FIG. 1;
FIG. 3 is a cross-sectional view taken along the line III--III
of FIG. 2 however, only an upper half thereof is illustrated;
FIG. 4 shows the tip of the suture needle according to the second
embodiment of the present invention;
FIGS. 5a and FIG. 5b show the tip of the suture needle according
to the third embodiment of the present invention;
FIG. 6 is a diagram for explaining a method of measuring impalement
resistance of a suture needle;
FIGS. 7 and 8 are graphs showing impalement resistance of the suture
needles according to the present invention and conventional suture
needles.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereafter, embodiments of the suture needle according to the present
invention will be explained with reference to the drawings.
A suture needle A shown in FIG. 1 is a round needle, and a base
end portion 2 engaging a suture thread 1 is provided at an end of
the needle, and a blind hole 2a is drilled at the base end portion
2 in an axial direction of the needle, where the suture thread 1
is to be inserted and fixed.
At another end of the needle, a tapered portion 3 of which a diameter
becomes larger as parting from a tip 3a is provided. The "tapered
portion" used here is, as described above, defined to be a
general shape of which a diameter or cross-section increases as
parting from the tip of a needle. In this case, the change of the
cross-section may be linear, as a matter of course, or curvilinear.
A portion between the base end portion 2 and tapered portion 3
is a body 4 of which diameter is substantially constant. In case
of a round needle, the body 4 has a round cross-section, but ordinarily,
two planes (planar surfaces) 4a, 4a which are in parallel with each
other are formed through press working so that the needle is easily
sustained by a needle-carrier at suturing work. Further, it is possible
to provide four planes to form a square shape, which causes the
needle to be more easily sustained and the strength of the needle
to be increased.
Although the above is also applied to a conventional round needle,
a round needle according to the present invention is characterized
in that a stripe rough surface 6 of which stripes direct in a substantially,
axial direction of the needle through grinding, is provided on the
tapered portion 3. It should be noted that the strip rough surface
6 is provided only on the tapered portion 3.
FIG. 3 is an enlarged view of the tapered portion 3 of the suture
needle shown in FIG. 2. As illustrated, the tapered portion 3 is
provided with the stripe rough surface 6. This stripe rough surface
is preferably formed by a whetstone regulated in ISO #30 to #320
a grinding belt, or the like. Further, the roughness of the stripe
rough surface is preferably more than twice as rough as that of
a mirror surface.
In the suture needle according to the above embodiment, when a
tissue is pierced at a predetermined portion by the tip of the needle,
a small clearance is formed between the stripe rough surface 6 and
the tissue, so that the area where the stripe rough surface 6 and
the tissue contact with each other decreases, allowing the tissue
to be impaled by the suture needle with less force. Since the clearance
is very small, and it is formed only when the tapered portion of
the needle proceeds, which securely prevents body fluids from leaking
after the proceeding of the needle, unlike the conventional one.
Further, the size of the stripe roughness is larger than those formed
by chemical polishing. With the crater-like roughness formed by
chemical grinding, such fine clearances as described above are not
generated, therefore, it is hardly expected to reduce the impalement
resistance.
In this connection, the width or depth of the stripe roughness
may freely be adjusted by selecting the number of abrasive grain
for grinding and machining conditions. Further, when the stripe
rough surface 6 is too rough or feel roughness after the grinding,
it is preferable to slightly carry out a process of buff finishing,
electrolytic polishing, chemical polishing, or the like after the
grinding to smooth the stripe roughness.
FIG. 4 shows a suture needle according to the second embodiment
of the present invention. In the above-mentioned embodiment, burrs
formed at the machining with abrasive grain causes the tip of a
needle not to be formed sharp. Then, only a tip portion 3b is formed
to be mirror surface like the conventional one. Finishing method
is selected from the buff finishing, electrolytic polishing, and
chemical polishing. Further, the length l of the tip portion to
be mirror finished is preferably about 5% to 20% of the length L
of the tapered portion 3.
FIGS. 5(a) and 5(b) show a suture needle according to the third
embodiment of the present invention. In this embodiment, only a
tip portion 3c which is mirror finished as shown in FIG. 4 is formed
to be a pyramid shape. Each edge 3d of the pyramid functions as
a cutting edge to open a tissue and reduce the impalement resistance.
However, this cutting edge is formed only on the tip portion 3c,
and after the tip portion 3c enters the tissue, the stripe rough
surface 6 impales the tissue. In this manner, the pyramid is formed
only on a limited tip portion of the suture needle to eliminate
a harmful influence that the tissue is cut too widely like the convention
square needle, and moreover, the initial impalement resistance can
be decreased.
In all the embodiments, conventionally used silicon treatment is
preferably applied. With the silicon treatment, silicon enters the
stripe roughness, so that the silicon is adequately maintained,
which prevents the increase of the impalement resistance after repeated
use of the suture needle.
FIG. 6 is a drawing for explaining a method of measuring the impalement
resistance of the suture needles according to the present invention.
The suture needle A is maintained in a straight shape before bending,
and is cramped by a vertically movable chuck 10. The chuck 10 is
provided with a load cell 11. An upwardly opened box 12 is located
below the suture needle A, and the opening of the upwardly opened
box 12 is covered by an impalement material 13 (such as polyurethane
with a thickness of 0.45 mm or a film-shaped "porvair"
with a thickness of 1.10 mm made by Dow Corning Co.).
The chuck 10 is lowered by a driver (not shown), and the tip 3a
of the suture needle A impales the impalement material 13. At this
moment, the impalement resistance is measured by the load cell 11.
FIGS. 7 and 8 are graphs indicating the impalement resistance measured
by the instrument illustrated in FIG. 6 when conventional suture
needles and the suture needles according to the present invention
are used. Solid lines show the impalement resistance when suture
needles according to the present invention are used, and dotted
lines show those of conventional suture needles. The suture needles
according to the present invention have a stripe roughness (ground
by the whetstone regulated in ISO #50) at a tapered portion, and
a top is mirror-finished, and after that, chemical polishing is
applied to the overall suture needle. The conventional suture needle
is mirror-finished at an ordinary tapered portion thereof through
buff machining, and after that, chemical polishing is applied to
the overall suture needle.
The suture needles shown in FIG. 7 are not subject to silicon treatment,
but the suture needles in FIG. 8 are treated by silicon ("MDX-4159"
made by Dow Corning Co.) after the same process to the suture needles
of FIG. 7. The depth (surface roughness) of the stripe of the suture
needle according to the present invention is approximately in the
range of 2 .mu.m-15 .mu.m. In contrast, the surface roughness of
the mirror surface of the suture needle is approximately in the
range of 0.2 .mu.m-0.5 .mu.m.
The suture needles without silicon treatment impaled the impalement
material 13 five times, and the impalement resistance at each impalement
was measured with the load cell. The suture needles with the silicon
coating impaled ten times, and the impalement resistance at each
impalement was measured.
In the both cases of FIGS. 7 and 8 it is clearly recognized that
the suture needles according to the present invention are superior
to the conventional suture needles. Especially, as shown in FIG.
8 there is not much difference between the both suture needles
with the silicon coating until four impalements. However, after
that, the difference between the present invention and conventional
technology becomes larger as the number of impalements increases.
This is because the repeated impalements causes the silicon applied
to the conventional suture needle to gradually be peeled off, while,
in the present invention, the silicon is sustained on the stripe
roughness and the effect of the silicon treatment continues.
Although the above explanation is made for a round suture needle,
it is possible to form the stripe roughness through grinding according
to the present invention to tapered portions of a square needle
and a dull needle and the same effects of the invention can be obtained.
Further, the same effects can be obtained even if the engaging portion
with a suture thread is a blind hole or a spring eye; the shape
of cross-section of a body was oval or a cross-section which is
sandwiched between two substantially parallel planes and a central
portion is constricted; and the needle is bent or straight. However,
the advantage of the present invention is most effectively achieved
when the suture needle is not provided with cutting edge at a tapered
portion thereof.
As described above, with the present invention, a suture needle
comprising a base end portion, at an end of the suture needle, engaging
a suture thread, a tip, at another end, impaling a tissue, a tapered
portion reaching to the tip, is characterized in that the tapered
portion is provided with stripe roughness through grinding, so that
small clearances are formed between the stripe roughness and the
tissue, resulting in decrease of the impalement resistance.
Although only a preferred embodiment is specifically illustrated
and described herein, it will be appreciated that many modifications
and variations of the present invention are possible in light of
the above teachings and within the purview of the appended claims
without departing the spirit and intended scope of the invention. |