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BACKGROUND OF THE INVENTION
The present invention relates generally to hollow needles, and, more
particularly, to the needle portion of hypodermic needles and the like for
penetrating various tissues to inject drugs, medicine, etc., to implant
conductor wires or other similar structures or to carry out any other
appropriate biomedical function.
It is, of course, well known that great progress continues to be made in
the medical sciences. New drugs are constantly being developed to treat or
cure diseases, and medical problems once thought to be incurable are now
routinely treated. Moreover, surgical techniques have reached such a high
level of advancement and sophistication that there almost seems to be no
limit to the type of tissue repair which can be achieved.
However, in all the years of progress in medicine, there has been virtually
no change in one of the principal tools of the medical profession--the
hypodermic needle. Basically, the hypodermic needle includes a relatively
thin, straight, hollow tube coupled at one end to a syringe of one type or
another. The other end is formed with a bevel of about 17.degree. to form
a sharp point, with the leading tip of the needle point being along the
longest side of the needle tube.
The hypodermic needle has always performed its function of injecting drugs,
medication or the like into the desired subcutaneous tissue. However,
there is one universally recognized drawback to the hypodermic needle as
it is currently constructed. A certain degree of trauma is suffered by the
tissue(s) penetrated by the needle, due to tissue coring and/or shaving.
Thus, in conventional needles with the usual beveled tip, the coring effect
results in a plug-like piece of tissue being cut-out and becoming wedged
inside the needle tube. In addition, the shaving effect caused by the
sharp recessed edge of the needle point (sometimes called the heel of the
bevel) results in thin slices of tissue being cut during penetration and
becoming lodged in the needle tube. For needles of very small tube
diameter, the trauma often causes only a little discomfort, usually in the
form of a dull pain which lasts a day or so after the injection. However,
the larger the needle size, the greater the trauma, particularly that
resulting from coring.
The tissue core and shavings will be ejected from the needle tube when
fluid is released from the syringe, so they do not usually interfere with
the fluid injection. However, it has recently been suspected that as these
discharged tissue particles decompose, particularly when injected into the
blood stream, there is a risk of developing certain types of cancer.
One design for eliminating the tissue coring and shaving effects,
particularly in larger needles, involves placing a sharply pointed rod
(often called an obturator) inside the needle tube with the sharp end of
the obturator projecting beyond the tip of the needle (which need not,
therefore, be beveled to form a sharp point). The obturator fairly well
blocks the hollow needle tube during penetration by the needle, and is
removed once the needle tip is at the desired depth in the tissue.
However, this arrangement entails the extra expense of fabricating the
obturator to fit the needle tube. Furthermore, in use, it necessarily
involves the additional steps of removing the rod and safely coupling the
syringe to the needle tube, and, when used in coronary assist procedures,
inserting a pacer wire (i.e., a helio coid) or other conductor wire
through the needle tube. In emergency or critical procedures, the time
lost by performing these additional steps could be critical.
Accordingly, it is an object of the present invention to provide new and
improved needle structures for hypodermic needles and the like and methods
for making a needle. It is another object of the invention to provide new
and improved needle structures for hypodermic needles and the like, and
methods for making a needle, which is capable of easier penetration into a
patient's tissue with minimum trauma.
It is also an object of the invention to provide new and improved needle
structures for hypodermic needles and the like, and methods for making a
needle, which substantially reduces and can virtually eliminate the coring
and shaving effects experienced with conventional hypodermic needle
constructions. Furthermore, the present invention is intended to be
capable of embodiment in virtually any size needle for uses ranging from
routine injections to precision injection/implantations such as in
coronary assist procedures. In addition, the needle of the present
invention can be embodied in otherwise conventional needle structures.
Objects and advantages of the invention are set forth in part herein and in
part will be appreciated herefrom. However, these and other objects and
advantages of the invention may be learned through practice with the
invention, the same being realized by means of the structures,
instrumentalities, steps, methods and combinations disclosed and claimed
herein. The invention thus resides in the novel constructions,
arrangements, steps, operations, combinations and improvements herein
shown and described.
SUMMARY OF THE INVENTION
Briefly described, a needle structure for hypodermic needles and the like,
and method of making a needle, according to the present invention includes
forming the beveled, sharply pointed free end of a thin, hollow needle
tube so that the leading tip at the beveled end shields, at least
partially, the hollow central portion of the needle tube. Advantageously,
a portion of the needle tube behind the needle point diverges relatively
slightly from the remainder of the needle tube so as to orient the leading
tip at a slight angle with respect to the remainder of the needle tube
such that it covers at least a portion of the hollow needle tube. As
preferably embodied, the divergent portion is formed as a slightly arcuate
segment in the needle tube just behind the needle point, which can
resemble a symmetrical bulge-like formation in the needle tube.
Alternatively, the divergent portion can be a relatively small single bend
in the needle tube. In a particularly useful embodiment, the present
invention can be a relatively large diameter (e.g., about 0.045") needle
for use in coronary assist procedures, with a helio coid conductor wire
already located within the hollow needle tube during penetration.
It will be apparent from the foregoing general description that the objects
and advantages of the invention specifically enumerated herein are
achieved by the invention as herein disclosed. Thus, for example, by
forming the needle so that the leading tip at the needle point shields at
least a portion of the hollow needle tube, it will be found that the
phenomenon of tissue coring during penetration of the needle is
substantially reduced, and even eliminated depending on the relative
angular inclination of the tip, thereby causing negligible trauma during
injections with even the largest diameter needles. In addition, the
shaving of tissue during penetration is equally reduced or eliminated in
needles formed in accordance with the present invention, because less
tissue is exposed to the sharp edge at the heel.
It will also be found that by forming a divergent portion behind the needle
point, the present invention can be embodied in an otherwise conventional
needle structure. Moreover, by forming the divergent portion as a curved
segment behind the needle point, it will be found that the reduction or
elimination of trauma is achieved without any appreciable loss of strength
of the needle or risk of needle fragmentation.
Furthermore, needles fabricated in accordance with the present invention
can be made on conventional equipment, without any significant increase in
manufacturing costs.
It will be understood by those skilled in the art that the foregoing
general description and the following detailed description are exemplary
and explanatory of the invention and are not intended to be restrictive
thereof. Accordingly, the accompanying drawings illustrate preferred
embodiments of the invention and, together with the following detailed
description, serve to explain the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A and 1B are illustrations of the current configuration for the
needle portion of conventional hypodermic needle assemblies, showing the
coring/shaving phenomenon when penetrating tissue (FIG. 1B).
FIG. 2 is a view, from the side, of a needle member for hypodermic needles
and the like made in accordance with the present invention.
FIG. 3 is a view, from the side, of part of a modified embodiment of a
needle made in accordance with the present invention.
FIG. 4 is a view, from the side, of part of a needle made in accordance
with the present invention, showing alternate angular configurations for
the needle tip.
FIGS. 5A, 5B and 5C are side views showing, in sequence, a comparison of
penetration of a conventional needle (the "PRIOR ART NEEDLE") and a needle
made in accordance with the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Referring first to FIGS. 1A and 1B and, in part, to FIGS. 5A thru 5C, there
are shown various illustrations of a conventional configuration for the
needle portion of a hypodermic needle assembly. A relatively thin, hollow
needle tube 10 (with a hollow interior indicated at 12) is beveled at one
end to form a sharp point at the leading tip 14, with a sharp edge 16 at
the heel of the bevel. The other end of needle tube 10 is attached by
conventional means to a hub 18 which either can form part of or be adapted
for attachment to a syringe or like member (not shown).
Although the point of needle 10 is shown to have a straight bevel, some
needle points are formed with a slightly concavely shaped bevel. In either
event, the angle (indicated by .alpha.) formed at the leading tip is
generally about 17.degree. in order to ensure sufficient structural
strength in the needle tip to prevent fragmentation of the tip. It will be
understood that as the bevel angle at the leading tip is reduced below
17.degree., the risk of fragmentation increases, unless resort is made to
very expensive high strength materials.
Since the tissue cutting is done primarily by the beveled edge portions of
the needle tip (the smooth cylindrical side of the needle essentially
glides through the tissue), the effective needle point angle to which the
tissue is exposed is the same as the angle of beveling. Thus, it is
desirable to reduce the angle of the needle point to reduce the trauma,
but conventional needles are limited in this regard because of the
increased risk of needle fragmentation.
FIGS. 1B and 5A through 5C illustrate the trauma caused to tissue 20 during
penetration of conventional hypodermic needles. Regardless of the size of
the needle, there is always a certain amount of tissue shaved (as
indicated at 22) by the heel (or recessed needle edge) 16 of the needle.
The tissue shaving results because the heel edge 16 is necessarily
sharpened to virtually the same degree as the needle point when the needle
point is machined to form the beveled tip. The sharp edge thus shaves off
thin slices of tissue (indicated at 22) during penetration and also leaves
behind a jagged path (indicated at 23) in the tissue.
Another problem with conventional needles, particularly larger diameter
needles, is the coring effect. Since the tissue penetrated by the needle
is directly exposed to the open hollow center of the needle tube, a core
or plug-like piece of tissue (indicated at 24) will become embedded in the
needle tube, resulting in significant trauma. Coring is most serious in
coronary assist procedures, because part of the heart tissue is actually
removed, leaving a hole in the heart which could result in serious
internal bleeding.
Turning then to FIGS. 2-4, there are shown various embodiments of the
improved needle construction according to the present invention for
hypodermic needles and the like. As shown in FIG. 2, the needle according
to the invention is virtually identical to conventional needle in every
aspect except as explained below. Thus, as an advantage achieved by the
invention, the needle can be made of the same materials, and it has a
thin, hollow needle tube 30 (with interior hollow portion 32), with its
leading tip 34 beveled to form a sharp point and a recessed heel edge 36.
It may also be attached to a hub 38 similar to hub 18 described above with
respect to FIGS. 1A and 1B.
According to the invention, a portion of the needle behind the point is
formed so that the outer cylindrical-like portion of leading tip 34 forms
a relatively small angle with respect to the remainder of that side of the
needle tube. As a result, there is a reduction in the effective cutting
angle (i.e., the angle .beta. in FIG. 2) to which the tissue is exposed
during penetration of the needle. In addition, and of high significance,
the leading tip shields at least a portion of the cross-sectional area of
hollow tube chamber 32, if not the entire area of interior chamber 32, so
that the coring effect of conventional needles is significantly reduced or
completely eliminated. Furthermore, the inclined leading tip also acts to
shield tissue from the sharp heel edge 36 so that the tissue shaving and
the jagged tissue path is likewise greatly reduced or eliminated. Thus,
the trauma caused by penetration of the needle is virtually eliminated or
at least significantly reduced, even for the largest diameter hypodermic
needles.
As embodied in FIGS. 2 and 4, the shielding configuration of the leading
tip is provided by forming a divergent portion 40 in the needle tube
behind the needle point. The divergent portion is proportioned so as to
terminate at or very near the leading tip of the needle and thereby orient
the leading tip at the desired angular inclination. As shown in FIGS. 2
and 4, both ends of the divergent portion are generally on-line with the
remainder of the needle tube so that the divergent portion resembles a
small symmetrical bulge in the otherwise straight needle tube. That is,
the divergent portion 40 is formed in a symmetrically arcuate
configuration to ensure virtually no loss in the structural strength or
integrity of the overall needle structure or the needle tip.
FIG. 4 illustrates the various orientations of the leading tip which can be
made in needles according to the present invention. Advantageously, the
divergent portion 40 is proportioned so that the resultant angular
inclination of the leading tip portion brings the point of leading tip 34
down generally to a point on the longitudinal axis (indicated by ) of the
needle tube, thereby reducing by about one-half the effective angle of the
needle point to which the tissue is exposed during penetration (i.e., from
an angle of about 17.degree. to an angle of about 8 1/2.degree.) without
requiring the much more expensive high strength materials. The needle
point may even be brought below the center line of tube 30, as indicated
at 34', down to a point where it completely shields the open interior
needle chamber 32 (i.e., when it is about even with or below the heel edge
36).
Advantageously, for needles 0.045" in diameter, the length of divergent
portion (as indicated at l in FIG. 4) is about 1/2", as measured between
the points p which are generally co-linear with the lower side of the
needle tube. It should be proportionately smaller for smaller diameter
needles. The depth of the deviation in the needle tube (indicated at d in
FIG. 4) may range from approximately 1/4 to about 1/2 the outer diameter
of the needle tube.
As shown in FIG. 3, the divergent portion (indicated at 40') can be formed
by making a single, relatively small bend near the point of the needle
tube. In order to ensure that the force applied to insert the needle is
directly behind the point, it is preferred that the divergent portion 40'
be proportioned such that the point 34 is generally within the projected
cross-sectional area of the remainder of the needle tube 30. In either
embodiment, the divergent portion is preferably formed without any kinking
so that opposite sides of the needle tube remain approximately the same
distance apart throughout the entire length of the tube, thereby avoiding
any tube restriction which might otherwise interfere with full functioning
of the needle assembly.
It will be understood that the divergent portion (40 or 40') can be made by
any suitable device such as a forming tool which will support the tube
side walls or otherwise prevent any significant kinking. The divergent
portion may also be formed during the drawing operation for forming the
needle tube itself, while the needle is still soft. Thus, it will be
appreciated that fabrication of needles according to the present invention
can be carried out as part of the fabrication of conventional needles,
with no significant increase in fabrication costs and without making
fabrication any more complex.
FIGS. 5A-5C illustrate the principal causes of trauma during needle
penetration (the coring effect resulting from the sharp beveled edge
portions at the leading edge and the shaving effect caused by the sharp
heel edge with resultant jagged path) and the advance embodied in the
needle according to the invention. It will be understood that the smooth
surface of the needle tube, in essence, glides past the tissue once
penetrated by the point of the needle tip. This is illustrated by the
relatively smooth tissue lines above both needles shown in various stages
of penetration in FIGS. 5A-5C.
However, during penetration of a conventional needle (indicated by "PRIOR
ART NEEDLE"), the trauma is evident from the abruptly disrupted and the
jagged tissue lines just below the recessed heel portion of the needle
bevel, as illustrated in FIGS. 5B and 5C. In contrast, the needle of the
present invention (the lowermost needle shown in each of FIGS. 5A thru 5C)
generates little or no trauma, as indicated by the much smoother curvature
of tissue lines below the needle. Because muscle and fat tissue are
somewhat pliable and resilient and because such tissue is essentially
self-lubricating, the tissue will follow the curved contour of the
divergent curved segment 40 without marked tissue disruption.
In a particularly useful embodiment of the present invention, the divergent
segment (40 and 40') can be formed on the needle portion of a hypodermic
needle assembly for use in coronary assist procedures. As here preferably
embodied, the needle portion according to the invention can simply be
adapted for use as part of the coronary assist package known as
Transthoracic Pacer, sold by Electro-Catheter Corporation of Rahway, N.J.
As so embodied, the insertion of the needle into the heart chamber for
injection of adrenaline and implantation of a helio coid pacer wire into
the heart can be carried out in a relatively simple procedure.
Accordingly, the helio coid wire can already be located inside the needle
tube with the curled end of the wire just behind the opening of the needle
bevel while the needle actually penetrates the patient's chest and heart.
There will be virtually no trauma, particularly that which would otherwise
be caused by the coring effect. Thus, the need for additional structure in
the form of an obturator, and the extraneous steps incident to its use,
are avoided by the present invention.
It is preferred that the divergent needle portions be proportioned so that
the cylindrical-like exterior surface of the leading tip be generally
smooth and straight to minimize any possibility of resistance to
penetration due to its angular orientation. In addition, the point of the
leading tip should be located essentially within the projected
cross-sectional area of the outer surface of the straight portion of the
needle tube so as not to effectively enlarge the cross-sectional area of
the needle tube.
It will be readily appreciated by those skilled in the art that the present
invention is not limited to the specific embodiments herein shown and
described. For example, the step of forming the divergent needle segment
can be carried out on a non-beveled needle tube and the beveling carried
out by a subsequent grinding operation. In addition, the hypodermic needle
according to the present invention can be used for implantation or like
procedures other than coronary assist procedures, where the coring effect
in large diameter needles would otherwise have precluded the use of a
needle to carry out the implantation. Thus, variations may be made within
the scope and spirit of the accompanying claims, without sacrificing the
principal advantages of the invention.
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