Surgical needle abstract
An improved surgical needle of the type having one or more cutting
edges converging towards the needle tip and formed by the intersection
of a plurality of planar surfaces, for use in cutting through hard
body tissue material. The forward end of the needle has one or more
smaller additional cutting edges located at the tip to aid initial
insertion into the tissue. These additional cutting edges are formed
by at least two additional intersecting planar surfaces at the tip
portion. The needle is preferably curved in the reference plane
defined by one of the cutting edges and the axis of the needle.
Surgical needle claims
I claim:
1. A surgical needle, comprising a body portion, a contiguous cutting
portion which terminates near the tip of the needle and a tip portion,
there being a plurality of planar surfaces forming cutting edges
in said cutting portion, which cutting edges converge towards the
tip of the needle, there being at least two additional planar surfaces
intersecting in the tip portion of the needle forming additional
cutting edges at the intersection between said additional planar
surfaces and at intersections between said additional planar surfaces
with selected ones of said plurality of planar surfaces.
2. The needle of claim 1 in which the cutting portion has top
and bottom surfaces, there being first, second and third intersecting
planar surfaces forming three cutting edges in said cutting portion,
the first and second planar surfaces being formed on the bottom
of said cutting portion and defining a first cutting edge, and the
third planar surface being formed on the top of said cutting portion
and defining second and third cutting edges.
3. A surgical needle, comprising a body portion having upper and
lower surfaces and a contiguous cutting portion which terminates
at a tip portion of the needle, said cutting portion having top
and bottom surfaces which are contiguous, respectively to said upper
and lower surfaces of said body portion, there being first, second
and third intersecting planar surfaces forming three cutting edges
in said cutting portion, which cutting edges converge towards the
tip of the needle, said bottom surface comprising said first and
second planar surfaces defining a first cutting edge which has a
forward end contiguous to said tip portion and a rear end, and the
third intersecting planar surface defining said top surface which
has second and third cutting edges; said tip portion having fourth
and fifth intersecting planar surfaces forming three additional
cutting edges, the intersection of the fourth and fifth planar surfaces
defining a fourth cutting edge which extends from the forward end
of said first cutting edge to the tip of the needle, the intersections
of said fourth and fifth planar surfaces with said top surface defines
respectively fifth and sixth cutting edges which converge to the
tip of the needle, the apex angle between the fifth and sixth cutting
edges being greater than the apex angle between the second and third
cutting edges.
4. The needle of claim 3 at least a portion of said body portion
of said needle having a curved longitudinally extending axis defining
a "reference plane", said first cutting edge being colinear
to a line in said "reference plane", said "reference
plane" being substantially perpendicular to said top surface,
said upper and lower surfaces of said body portion being curved.
5. The needle of claim 4 wherein both the first and the fourth
cutting edges lie in said "reference plane".
6. The needle of claim 5 wherein the third planar surface is positioned
such that a straight line "L" (which is formed by the
intersection of the reference plane and said third planar surface)
is colinear with the immediately contiguous curved line "M"
formed by the intersection of the "reference plane" and
the upper curved surface of said body portion, said straight line
"L" constituting a tangent to curved line "M",
so that if said body portion were to be straightened, said line
"L" would be parallel to said axis.
7. The needle of claim 5 wherein the angle of slope of the forth
cutting edge is less than 45.degree., said "angle of slope"
being defined as the angle between said cutting edge and said top
surface, in said "reference plane".
8. The needle of claim 7 wherein the angle of slope of the fourth
cutting edge is between 30.degree. and 37.degree..
9. The needle of claim 4 wherein the angle of slope of the first
cutting edge is between 8.degree. and 20.degree., said "angle
of slope" being defined as the angle between said cutting edge
and said top surface, in said "reference plane".
10. The needle of claim 9 wherein the angle of slope of the first
cutting edge is between 11.degree. and 13.degree..
11. The needle of claim 4 said axis being curved in a circle having
a given radius and a given center, said lower surface being located
on the inside of the needle radius so that said lower surface is
closer to said center of said circle than is said upper surface,
portions of both the upper and lower surfaces of said body portion
being flattened to increase needle holder stability.
12. The needle of claim 4 said axis being curved in a circle having
a given radius and a given center, said lower surface being located
on the outside of the needle radius so that said upper surfave is
closer to said center of said circle than is said lower surface,
portions of both the upper and lower surfaces of said body portion
being flattened to increase needle holder stability.
13. The needle of claim 11 or 12 in which grooves are formed in
said flattened surfaces of said body portion for additional needle
holder stability.
14. The needle of claim 3 wherein the apex angle between the second
and third cutting edges is between 10.degree. and 25.degree..
15. The needle of claim 14 wherein the apex angle between the
second and third cutting edges is between 12.degree. and 15.degree..
16. The needle of claim 3 wherein the apex angle between the fifth
and sixth cutting edges is between 30.degree. and 60.degree..
17. The needle of claim 16 wherein the apex angle between the
fifth and sixth cutting edges is between 30.degree. and 45.degree..
18. The needle of claim 3 wherein the angle between the fourth
cutting edge and the line formed by the intersection of the first
and fourth planar surfaces is between 30.degree. and 130.degree.
included.
19. The needle of claim 18 wherein the angle between the fourth
cutting edge and the line formed by the intersection of the first
and fourth planar surfaces is between 60.degree. and 110.degree..
20. The needle of claim 3 wherein the "dihedral angle"
between the first and second planar surfaces is between about 50.degree.
and 70.degree..
21. The needle of claim 20 wherein the "dihedral angle"
between the first and second planar surfaces is between about 55.degree.
and 65.degree..
22. The needle of claim 3 wherein the "dihedral angle"
between the fourth and fifth planar surfaces is between about 50.degree.
and 70.degree..
23. The needle of claim 22 wherein the "dihedral angle"
between the fourth and fifth planar surfaces is between about 55.degree.
to 65.degree..
Surgical needle description
FIELD OF THE INVENTION
This invention relates to surgical needles and in particular to
an improved surgical needle for suturing through calcified tissue,
cartilage or bone.
DESCRIPTION OF THE PRIOR ART
Surgical needles are required to be as sharp as possible at the
tip in order to perform their function properly. Such needles must
also be resistant to burr formation caused by an insufficient amount
of metal at the extreme tip portion of the needle. In the Kurtz
U.S. Pat. Nos. 2869550 and 3094123 a sharp surgical needle
was disclosed, which needle has a single main cutting edge formed
by the intersection of two planar surfaces such that the main cutting
edge extends from one side of the needle to the other side thereof.
In this type of needle greater sharpness is obtained by decreasing
the slope angle of the main cutting edge relative to the needle
axis. However, as discussed in Kurtz U.S. Pat. No. 3636955 as
the slope angle is decreased, eventually, so little material is
left at the point that the point lacks sufficient structural integrity
to effectively penetrate the tissue without the tip of the point
burring or otherwise deforming.
In the Kurtz U.S. Pat. No. 3094123 the concept of blunting the
tip of the needle to avoid deformation of the tip, even when using
a fairly sharp slope angle, was disclosed. The Kurtz U.S. Pat. No.
3636955 discloses the concept of adding a third planar surface
at the extreme tip so as to form a chisel-type cutting edge at the
intersection of the third planar surface with one of the first two
planar surfaces. However, as the structural strength of the tip
portion of the needle has been increased by providing more metal
at this area by using either a rounded tip or a chisel-type tip,
the amount of force to obtain needle penetration has been increased
particularly when calcified tissue has to be penetrated. Thus, there
is a need for a surgical needle having a very sharp point but which
is still strong enough to retain its structural integrity when used
to cut through bone or other hard tissue.
The amount of force required for needle penetration of tissue includes
that required for the engagement of the tip of the needle and for
the widening of the hole. The widening of the hole is effected either
by the blunt dilatation of a conventional taper point needle or
by a very sharp cutting action. In the case of a taper point needle,
after the tip is engaged, a hole is made by pure blunt dilatation
with no cutting action whatsoever. Alternatively, using a needle
of the type disclosed in Kurtz U.S. Pat. No. 2869550 a hole is
produced by initially engaging the tip. The cutting edge of this
needle then enlarges the hole and finally the remainder of the hole
size is made by blunt dilatation with no cutting edge being present.
When the hole is fully developed, the rest of the shaft slides through
with friction as the major resistance component. Furthermore, with
a conventional cutting edge needle, the relatively sharp edges slide
through after the tip is engaged, until there is a fully developed
hole. The dilatation per unit time is a direct reflection of the
work required, and hence the force required for the needle to make
the fully developed hole. With a taper point, the included angle
(at the apex of the cone) is approximately 12.degree.. When the
needle's included angle is more acute, less work per unit time would
be required to make a fully developed hole. However, the more acute
the angle, the more fragile the tip, with resultant possible bending
over and burr formation, which destroys the sharpness of the needle.
When the angle is greater than 12.degree., the dilatation per unit
time must be faster and the needle appears to be more blunt because
of the necessity for rapid dilatation. The longer the edge which
slips through tissue on entering, the sharper the needle and the
less required force per unit time to make a completely developed
hole. Furthermore, a sharper needle results in a smaller opening
and the minimization of trauma. Kurtz U.S. Pat. No. 4128351 is
directed to a surgical needle of the type having a single main cutting
edge formed by the intersection of two planar surfaces for use in
cutting through hard body tissue material. The latter patent discloses
a forward end of the needle which includes a single, relatively
small additional substantially planar surface having an acute angle
of convergence with the axis of the needle and intersecting at substantially
equal acute angles with the other two planar surfaces, resulting
in a sharp needle with a relatively high resistance to burring.
The Orcutt U.S. Pat. No. 3038475 discloses the concept of a triple
edged surgical needle, but does not address the problem of the burring
of the needle point.
One of the objects of the present invention to provide a triple
edged needle which is formed with three smaller additional cutting
edges located at the tip in order to aid initial insertion into
the tissue. It is a further object of the invention to provide a
flattened and ribbed section near the cutting portion of the needle
to facilitate positive placement and pick-up during needle penetration
through hard tissue.
The needle disclosed in Kurtz U.S. Pat. No. 4128351 being conventionally
ground on only two sides, has a portion of the needle circumference
remaining so that it contains only one main cutting edge (apart
from the small cutting edges at the forward end of the needle),
whereas the preferred embodiment of the present invention provides
three main cutting edges (apart from three smaller additional cutting
edges at the forward end of the needle). The tip of one of the embodiments
of the needle of Kurtz U.S. Pat. No. 4128351 terminates at the
intersection of the needle's centroidal axis and its main cutting
edge; whereas in the case of the present invention, the tip of the
needle terminates at the intersection of the main cutting edge and
the outer periphery of the needle.
Although the preferred needle of the present invention is triple
edged with three smaller additional cutting edges located at the
tip, nevertheless the invention includes needles formed with fewer
than three edges, and in which there are at least two additional
intersecting planar surfaces at the tip portion, forming one or
more additional cutting edges.
According to the present invention there is provided a surgical
needle comprising a body portion, an adjacent cutting portion which
terminates near the tip of the needle and a tip portion, there being
a plurality of planar surfaces forming one or more cutting edges
in the cutting portion, which cutting edges converge towards the
tip of the needle, there being at least two additional intersecting
planar surfaces at the tip portion of the needle forming one or
more additional cutting edges.
According to a preferred embodiment of the present invention, there
is provided a surgical needle comprising a body portion and an adjacent
cutting portion which terminates at the tip of the needle, the cutting
portion having top and bottom surfaces, there being first, second
and third intersecting planar surfaces forming three cutting edges
in the cutting portion, which cutting edges converge towards the
tip of the needle, the first and second planar surfaces being formed
on the bottom of the cutting portion and defining the first cutting
edge, and the third planar surface being formed on the top of the
cutting portion and defining second and third cutting edges. According
to the most preferred embodiment of the present invention, there
are fourth and fifth intersecting planar surfaces at the tip of
the needle forming three additional cutting edges, the fourth and
fifth planar surfaces being formed on the bottom of the cutting
portion and defining a fourth cutting edge which extends from the
forward end of the first cutting edge to the tip of the needle,
the fourth and fifth planar surfaces forming together with the third
planar surface, fifth and sixth cutting edges respectively, which
converge to the tip of the needle, the angle between the fifth and
sixth cutting edges being greater than the angle between the second
and third cutting edges. The angle of slope of the first cutting
edge is preferably less than 20.degree..
The side of the needle having the above metioned first or main
cutting edge is referred to herein as the "bottom" of
the needle and the plane defined by said main cutting edge and the
axis of the needle point or tip is referred to herein as the "reference
plane" so that when the main cutting edge is on the bottom,
the reference plane is vertical. By convention, the angle between
the main cutting edge and the upper, outer periphery of the needle
is termed the "angle of slope". This angle determines
the rate at which the tissues are cut, to the diameter of the needle.
The angle of slope must be minimized in order to provide for ease
of passage of the needle through the tissue and yet must be sufficiently
large to preserve metal at the point of the tip to give the needle
rigidity. In the present invention, it is preferable that the angle
of slope be less than 20.degree..
The needle of the present invention is preferably curved in the
reference plane defined by the first cutting edge and the longitudinal
axis of the needle. The fourth cutting edge which extends from the
first cutting edge should also lie in the reference plane. It is
furthermore preferred that the third planar surface be positioned
such that a fictive straight line "L" (which is formed
by the intersection of the reference plane and the third planar
surface), is substantially parallel to the central axis of the needle.
The angle of slope of the first cutting edge desirably varies between
8.degree. and 20.degree. (and more preferably between 11.degree.
and 13.degree.).
The angle between the second and third cutting edges should desirably
be between 10.degree. and 25.degree. (and more preferably between
12.degree. and 15.degree.).
The angle between the fifth and sixth cutting edges is desirably
between 30.degree. and 60.degree. (and more preferably 30.degree.
and 45.degree.). Furthermore, the angle between the fourth cutting
edge and the line formed by the intersection of the first and fourth
planar surfaces is desirably between 30.degree. and 130.degree.
(and more preferably between 60.degree. and 110.degree.).
The angle between the first and second planar surfaces is termed
the "sharpness angle and should desirably be between 50.degree.
and 70.degree. and is preferably between 55.degree. and 65.degree..
The preferred surgical needle of the present invention has three
long cutting edges formed by the intersection of three planar surfaces,
as well as three secondary edges presenting different angles located
near to the tip of the needle. This needle permits a long cutting
action and yet with much less likelihood of bending or deformation
of the tip. The foregoing and other objects and advantages of the
present invention are discussed in or will become apparent from
the detailed description of the preferred embodiment hereinbelow.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings, in which like numerals represent like elements
in the several views:
FIG. 1 is a bottom view of the cutting portion of a surgical needle
of the present invention.
FIG. 2 is a top view of the needle of FIG. 1.
FIG. 3 is a side view of the needle of FIG. 1.
FIG. 4 is a cross-sectional view taken along line 4--4 of FIG.
3.
FIG. 5 is a cross-sectional view taken along line 5--5 of FIG.
3.
FIG. 6 is a cross-sectional view taken along line 6--6 of FIG.
3.
FIG. 7 is a side view of a modified embodiment of the needle of
FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A surgical needle 40 according to the present invention, is illustrated
in FIGS. 1 through 6. Needle 40 includes a body portion 41 and a
cutting portion 42 and has a curved axis 43 (see FIG. 3) which defines
a reference plane. As will be seen from FIG. 7 (which shows a modified
embodiment of the needle of FIG. 1), the needle 40 may optionally
be curved in a direction opposite to that of the needle shown in
FIG. 3 and will have a curved axis 43' which nevertheless lies in
the same reference plane as that defined by axis 43 (as shown in
FIG. 3). A main cutting edge 21 is formed in a conventional manner
at the bottom of said cutting portion 42 by the intersection of
a first substantially planar surface 31 and a second substantially
planar surface 32 (FIG. 1). Thus it can be seen that main cutting
edge 21 lies in the reference plane as shown in FIG. 3. Secondary
cutting edges 22 and 23 are formed by the intersection of a third
substantially planar surface 33 (on the top of the cutting portion
42), with planar surfaces 31 and 32 respectively (FIG. 2).
Cutting portion 42 includes an end portion 50 and a tip 60 the
longitudinal axis of the needle being designated 43. Substantially
planar surfaces 34 and 35 are formed at the bottom of end portion
50 thus creating three additional cutting edges 24 25 and 26 (FIGS.
1 2 and 3). It will be noted that cutting edge 24 constitutes an
extension of cutting edge 21 (FIG. 3) and said cutting edge 24 extends
to the tip 60 which lies at the intersection of the reference plane
and planar surface 33 (FIG. 2). It will also be noted that the angle
"a" between cutting edges 25 and 26 is necessarily greater
than the angle "b" between cutting edges 22 and 23 (FIG.
2). Said angle "a" is between about 30.degree. and 60.degree.
and is preferably between 30.degree. and 45.degree.; whereas said
angle "b" is between about 10.degree. and 25.degree. and
is preferably between 12.degree. and 15.degree..
It will be noted from FIGS. 1 and 3 that the intersection between
planar surface 31 and planar surface 34 forms an edge 51; and the
intersection between planar surface 32 and planar surface 25 forms
an edge 52. The angle "c" between edge 51 and cutting
edge 24 is preferably between about 60.degree. and 110.degree. and
can range from about 30.degree. and 130.degree..
The angle of slope "d" between cutting edge 21 and planar
surface 33 (as measured along the reference plane) is less than
20.degree. and is preferably between 11.degree. and 13.degree..
the angle "e" between cutting edge 24 and planar surface
33 as measured along the reference plane is less than 45.degree.
and is preferably between 30.degree. and 37.degree..
It will be noted that the tip of the needle 60 lies in the planar
surface 33 and is thus displaced from the central axis 43 of the
needle. In this connection, the planar surface 33 is positioned
such that the fictive straight line "L" (which is formed
by the intersection of the reference plane and planar surface 33)
is substantially parallel to the central axis 43 (FIG. 3).
All of the planar surfaces 31 32 33 34 and 35 are preferably
formed, and then ground.
FIGS. 5 and 4 depict the cross-sectional shapes of needle 40 at
two locations along the body portion 41 and the cutting portion
42 (FIG. 3). Needle 40 is generally round in cross-section with
a flattened section at 44 and also at 45 to increase needle holder
stability. In this connection, elongated grooves 46 and 47 may also
be formed in the flattened portions 44 and 45 for additional stability.
Said grooves 46 and 47 are indicated in FIG. 2 and FIG. 1 respectively.
FIG. 5 depicts the cross-sectional shape of the needle, illustrating
the flattened portions 44 and 45 (see FIG. 3). Grooves 46 and 47
are also illustrated in FIG. 5.
FIG. 4 depicts the cross-sectional shape of the needle 40 at the
cutting portion 42. It will be noted that said cross-sectional shape
is substantially that of an equilateral triangle, so that the sharpness
angle between the first and second planar surfaces 31 and 32 is
between 55.degree. and 65.degree.. However, this sharpness angle
may be varied between 50.degree. and 70.degree.. The sharpness angle
is designated as "f" in FIG. 4.
FIG. 6 depicts the cross-sectional shape of needle 40 at the forward
tip thereof. The sharpness angle "g" desirably varies
between 50.degree. and 70.degree. and most preferably is between
about 55.degree. and 65.degree..
With respect to the sharpness angle "f" (FIG. 4) if it
should be made too small, there would be insufficient metal in the
forward end of the needle to give the point the necessary strength.
Similarly the angle of slope "d" (FIG. 3) should be minimized
in order to provide for ease of passage of the needle through the
tissue and yet must be sufficiently large to perserve metal at the
tip to give the needle sufficient rigidity. The needle of the present
invention 40 performs best when the sharpness angle is within the
range of 50.degree. to 70.degree. and is preferably between about
55.degree. and 65.degree..
The provision of the forward tip 50 (FIGS. 1 2 or 3), not only
provides additional independent cutting edges but enables the needle
40 to resist burring when it is used in hard tissue. At the same
time, however, the needle 40 has a low insertion and penetration
force requirement and thus creates a minimal amount of trauma.
STERNOTOMY PERFORMANCE COMPARISON;
Penetration through Polyurethane
In order to determine the relative ease of penetration of a polyurethane
pad, demonstrated by the present needle as compared to that demonstrated
by a needle such as that disclosed in the Kurtz U.S. Pat. No. 4128351
the following tests were conducted:
A polyurethane pad was mounted over an Instron load cell. Needles
which were handheld, were penetrated through the polyurethane pad
and the average peak forces were measured. The needle of the present
invention (60 mil), made of stainless steel was compared with a
Deknatel sternotomy, stainless steel needle, (60 mil), designated
K-60. Both types of needles were initially stripped clean and siliconed
so as to ensure that the lubrication was comparable in each case.
Five different needles of each type were tested and three tests
were conducted with respect to each. After averaging the results
of all of the tests, the average force required for the present
needle to penetrate the polyurethane pad was 7.9 pounds; whereas
the average force required for the Deknatel K-60 needle to penetrate
the same polyurethane pad was determined to be 11.45 pounds. Said
Deknatel K-60 needle is similar in shape to that shown in FIG. 5
of the aforementioned Kurtz U.S. Pat. No. 4128351. It will be
noted that it is not feasible to use an actual sternum for conducting
these tests, due to the lack of uniformity along its length. |