US 3071135 A
Description (OCR text may contain errors)
B. E. BALDWIN ETAL Jan. 1, 1963 HOLLOW NEEDLE 2 Sheets-Sheet 1 Filed Jan. 27, 1960 PRIOR ART PRIOR ART 1 Jan. 1, 1963 B. E. BALDWIN ETAL 3,071,135
HOLLOW NEEDLE EJ6112 2: r5 15:1 cu-e 675a zfduz z'r-z fay agz'rzoZer-zme /sy 2 a m 2 w Z T U n 1 A 6 3 R z a 2 N n w N EA W 8 WM E Q MM E0 2 mm E] E m o V m 9 m 7/ u .j m J d u m 0 3,071,135 HOLLQW NEEDLE Brian E. Baldwin and Ray S. Lindenrneyer, Evanston, IlL, assignors to Manufacturing Process Laboratories, inc, Chicago, 11th, a corporation of Illinois Filed Jan. 27, 196i), Ser. No. 4,985 3 Claims. (i.]t28-221) This invention relates to a hollow needle, and more specifically, to an improved and highly effective non-coring hypodermic needle.
The problems and possible dangers of coring in the use of hypodermic needles have come to light only in recent years. As a hypodermic needle penetrates a tissue layer or membrane, the sharp leading edges of the beveled point cut an arcuate slit and, if the flap defined by this curved slit gets into the path of the needles sharpened heel edges, a minute plug or core of tissue may be severed from the fiap. Such a core, if cut from a flap of skin, is likely to be transplanted in a muscle, vein or tissue under the skin, depending on the final position of the needle tip at the time of fluid injection. In effect, the core becomes a skin graft when transplanted into muscle or under-the-skin tissue and might produce a cyst or subcutaneous infection. In a case of venous injection, it is at least theoretically possible for the skin core to lodge in the tiny reins of the lungs, thereby causing an embolism.
Coring may also occur when a hollow needle is forced through the membrane of a vial or other container. In such a case, the small particle of rubber is either drawn into the lumen of the needle or drops downwardly into the vial. Even if the latter should occur, there is the danger that the detached core may later be drawn into the syringe as it is manipulated to withdraw the vials contents and, where a multidose vial is used, it is believed apparent that the likelihood of drawing such a core into the syringe and thereafter injecting it into a patient is considerably increased.
EiTorts have been made to develop non-coring needles but the results of such efforts have been generally unsatisfactory. For example, it has been thought that if the heels of needles were depressed slightly then the sharpened edges of those heels would pass through the arcuate openings cut by the needles leading edges and would not sever the tissue flaps or cut into the walls of the openings. However, the mechanical operation of physically depressing the heel of a small bore needle is an extremely delicate one and, at best, is a time consuming and expensive procedure requiring extreme precision and control. Furthermore, it has been found that mechanically depressing a needle heel does not in itself substantially reduce the coring tendency of that needle. Instead, it creates a new problem because of the constriction of the needle lumen and the resulting interference with the smooth flow of liquid therethrough.
Since a needle with a depressed heel has certain inherent disadvantages and does not efiectively solve the coring problem, some workers in the field have attempted to overcome the problem by a different operation wherein a needle is ground to provide a step or shelf in the area of its heel, the previously sharpened heel edges about the lumen opening being obliterated and the rising portion of the step providing a blunt forward face. Such a needle naturally requires increased force for penetration since the blunt surface ordinarily encounters considerable resistance upon engagement with the flap cut by the needles tip edges. Moreover, as far as coring is concerned, it has been found that even such a radical design as this not only has a tendency to core but also appears to abrade small particles from the outer surface of the flap as the needle is inserted.
hired rates Fatent HQC A problem somewhat related to coring and one which must also be considered in connection with needle point geometry concerns the effects upon needle penetration force characteristics incident to variations in needle point configuration. It has been found that when a conventional needle penetrates a membrane the force required for insertion increases until the outer perimeter of the needle heel passes through the membrane opening. From then on, no further expansion of the membrane opening is required for passage of the needle and the penetration force drops to a generally constant value. Since the maximum penetration force required for insertion of any given needle into tissue bears an important relation to the pain caused by such insertion, it is apparent that any changes in needle configuration intended to reduce the coring problem must not at the same time increase the needles resistance to penetration. Conversely, a noncoring needle is of little practical value if the structural changes responsible for its non-coring characteristics result in a relatively high penetration force peak.
Accordingly, a main object of the present invention is to provide a highly effective non-coring needle of simple and inexpensive construction which overcomes all of the aforementioned defects and disadvantages of previous needles. Specifically, it is an object to provide a noncoring needle in which the structural features responsible for preventing coring do not reduce its penetration characteristics, impair the flow of fluid through its lumen, or adversely affect its behavior in any other material respect. Another object is to provide an improved needle which will not abrade a membrane or tissue during insertion and which has a relatively low penetration force peak or maximum.
Other objects will appear from the specification and drawings in which:
FIGURE 1 is an enlarged plan view showing the end portion of a needle embodying the present invention; 1
IFIGURE 2 is a side elevational view of the needle illustrated in FIGURE 1;
FIGURE 3 is a further enlarged end elevational view showing the needle tip and heel construction;
FIGURE 4 is an enlarged cross sectional view taken along line 44 of FIGURE 1;
FIGURE 5 is a sectional view of a vial having a conventional needle (lancet) partially inserted through the membrane thereof;
FIGURE 6 is an enlarged longitudinal sectional view of a conventional lancet as it penetrates a relatively thick resilient membrane;
FIGURE 7 is a greatly enlarged longitudinal sectional view of a needle embodying the present invention, the View being taken along line 7-7 of FIGURE 1;
FIGURE 8 is a graph representing the force patterns for needle penetration of a membrane.
In the structure illustrated in the drawings, the numeral It) generally designates a hollow needle or cannula with a lumen ll of uniform cross section extending longitudinally therethrough. In the illustration given, the tubular needle is cylindrical in shape and the lumen is circular in cross section. At one end, the needle is provided with a beveled front face =12 while at its opposite end it may be provided with a suitable adapter 12a, indicated by broken lines in FIGURE 1, for connection to a hypodermic syringe.
As is well known in the art, a pointed needle is formed by first grinding or otherwise treating a tube of small bore so that its front face 12 lies along a plane angled with reference to the tubes longitudinal axis. Preferably, but not necessarily, the tube is then rotated about its longitudinal axis and is subjected to additional grinding or treating operations to dforin beveled side faces 13 angled with reference to the plane of the main face 12.
The side bevels result in the formation of a sharply pointed tip 14 and thereby reduces the force necessary for needle penetration. In the absence of the side bevels, the needle tip would be curved rather than pointed since it would constitute a portion of the outer elliptical perimeter of the main bevel 12. As far as the present invention is concerned, the needle may or may not be provided with side bevels although the provision of such bevels is desirable for the reason already given.
The portion of a needle face behind the midpoint of the lumen opening is generally referred to as the heel of the needle. It is the construction or configuration of heel surface 15, and its outer perimeter, as well as the inner perimeter or edge portion of that heel bordering the lumen opening 16, with which the present invention is concerned.
The conditions which give rise to coring are illustrated in FIGURES 5 and 6 of the drawings. FIGURE 5 shows a conventional lancet A as it penetrates the flexible diaphragm B of a vial C. The flap cut by the leading edges of the lancet flexes downwardly to accommodate the needle and, in so doing, bears against the rear heel edge of the downwardly moving needle. Should the heel edge of the needle cut into the membrane flap, a small plug of rubber may be detached from that flap and either pass into the needle lumen or drop downwardly into the vial.
The thickness, smoothness, toughness and flexibility of the membrane all have a bearing on the tendency to form detached plugs or cores upon needle penetration. For instance, if the membrane is relatively thin and flexible, the flap will be more likely to yield upon contact with the rear edge of the lumen rather than be out by that rear edge. On the other hand, if the diaphragm or tissue is relatively thick, as indicated in FIGURE 6, the heel edge of the needle may engage the outer surface of the membrane before a flap is completely formed with the result that the heel edge of the conventional needle A is more likely to cut or scrape the membrane directly in its path and thereby abrade particles from the membrane or form a detached plug of material.
Referring again to FIGURES l4 and 7 illustrating the needle vit embodying the present invention, it will be seen that heel is dished to provide an external recess '17. While this concavity might be referred to as a depression, it is important that there is no corresponding bulge or deformation beneath the heel within the needle lumen. Instead, the internal cross sectional dimensions of the needle remain uniform and the recess arises because some of the material from which the needle is formed has been removed from the heel.
The external recess 17 extends rearwardly a limited distance behind the rear edge portion 18 of the lumen opening 16 and, as shown most clearly in FIGURES 2, 3 and 7, rear edge portion 18 is rounded (when viewed in section) and dulled. The smoothly rounded surface of edge portion 18 merges with the smooth surface of heel recess 17 and the outer limits of the generally lozengeshaped recess merge smoothly and without sharp angles into the surface of planar face 12. Upon needle insertion, should contact occur between rear edge portion 18 and a tissue or membrane, the smooth dull surfaces of that edge portion will tend to slide over rather than scrape or cut into the membrane or tissue, thereby reducing the resistance to needle penetration which might otherwise be caused by sharpened rear lumen edges (FIGURE 6) and eliminating the dangers of plug cutting. Further, it will be noted that these important advantages are achieved without lumen constriction and the undesirable effects thereof.
While various means might be used to remove material from the heel and rear edges of the lumen opening, We have found that such an operation may be performed simply and quickly by the carefully cont-rolled application of any of a variety of commercial etchants. Etching also has at least one other important advantage in connection with the removing of metal from the needle heel and lumen edges; it leaves the recessed heel and the rounded edges of the lumen opening with smooth glass-like surfaces. Also, the recess surfaces merges smoothly with the rear lumen edges and with the remainder of the heel sunface so that there are no sharp edges or abrupt slope changes in the vicinity of the needle heel which might tend to cut or abrade the edge portions of an opening formed by insertion of the needle point.
Upon insertion of needle 10 into a tissue or membrane, the dull and smooth rear edges about the lumen opening slide over and push aside rather than cut the membrane or tissue so that no core is formed, even where the body wall or membrane is relatively thick as in FIGURE 6. The fact that a substantial portion of the heel surface as well as the rear edge of the lumen opening are spaced within the circumferential limits of the needle reduces to some extent the likelihood of contact between the tissue or membrane and surface 17 or edge portion 18. However, even when such contact occurs, the dull and smooth rear edges about the lumen opening tend to push the material away rather than out into or abrade the surface thereof.
Extensive tests have been undertaken which demonstrate the non-coring properties of a needle embodying the present invention and also showing its superiority in this regard over other needles known in the art. In one such test, a double side bevel needle (lancet) embodying the invention was compared with 26 other needles having different needle point geometry. Specifically, the needles with which comparison was made included needles having points with single bevels, double side bevels (lancets), single side bevels and back bevels. In addition, such needles had various other characteristics such as depressed heels, step-cut heels, deflected points (full and half bend) and different bevel angles. For test purposes, all needles were of increased size (10 magnification of 18 gage needles). Three inch squares of A inch thick rubber with a 50 durometer reading were placed in a frame and were punctured by each model needle. Three tests were made with each model pointfirst with three thicknesses of rubber, next with two pieces, and finally with one piece. When all tests were made, the resulting puncture configurations were studied and the size of core or the tendency to cut cores noted.
In the tests involving the needle embodying the present invention, no cores were cut at all. All of the remaining needles cut cores in at least one test of each test series, with the exception of one needle of the group of depressed heel lancets which made substantial cuts in the rubber flap with its lumen edges but did not completely detach the plug from that flap. In summary, the needle embodying the present invention was more effective by a considerable margin than any of the needles tested in its ability to penetrate without coring.
An important aspect of the present invention lies in the fact that, in addition to its non-coring properties, needle It) has a relatively low penetration force peak. Referring to the graph of FIGURE 8, solid line 20 represents a typical penetration force curve for a conventional hypodermic needle. The dip behind the first small pea" 21 represents the slight reduction in applied force which frequently occurs the moment the sharpened tip of the needle breaks through or cuts into a tissue or membrane. Thereafter, the force required for needle penetration progressively increases until the maximum force at peak 22 is exerted. This major peak in applied force occurs when the rear portion of the needle heel--that is, the outer rear perimeter of the elliptical main bevel or faceis about to pass through the opening in the membrane. As soon as the outer rear edge of the needle face passes through the opening, there is a drop in the force required for further needle movement through the opening.
Unlike a conventional needle, needle 10 of the present invention does not have an abrupt change in contour at a junction between the beveled heel surface and the cylindrical surface of the tubing. Instead, the rear surface portion of the main face 12 curves or blends smoothly into the tubular surface therebehind. In addition, the surface of the tissue flap recess 17 blends smoothly with the remainder of the heel surfaces and with the cylindrical surface of the needle behind face 12, the recess extending rearwardly into the cylindrical outer surface of the needle a substantial distance behind the beveled surface 12.
The blending of the heel surfaces with the needles cylindrical surface and the provision of the tissue fiap recess or groove 17 which relieves tension of the membrane flap results in a needle having a relatively low penetration force peak. This is represented in the graph of FIGURE 8 by broken line 23. It has been found that the maximum penetration force required for insertion of a needle embodying the present invention is substantially less than the maximum force for a conventional needle having the same bevel angles.
The importance of this difference in maximum penetration force becomes apparent when it is understood that pain of injection is associated with a pressure threshold. Unless a threshold force level is reached, a patient may feel no pain at all when a needle is inserted into his body. While this threhold value varies depending upon the area of injection and also varies for different individuals, it is nevertheless significant that a needle having relatively low maximum penetration force characteristics may in many instances produce painless injection.
It should be noted that the graph in FIGURE 8 represents the penetration force curves of needles as they penetrate a thin membrane, in contrast to relatively thick membranes or body tissues. The drop off in maximum penetration force does not occur until the heel of a needle has passed completely through the membrane or tissue and therefore, in the case of injection into a patients body, no reduction in the maximum force level would be expected until forward movement of the needle ceases.
While in the foregoing, we have disclosed an embodiment of the present invention in considerable detail for purposes of illustration, it will be understood by those skilled in the art that many of these details may be varied without departing from the spirit and scope of the invention.
1. A non-coring needle having a beveled front face and having a lumen of uniform cross section, said face providing a lumen opening of cross sectional dimensions no smaller than the cross section of said lumen, said face providing behind the lumen opening a heel surface merging with a smooth rounded and dull rear edge portion of said lumen opening, said heel surface also being dished to provide a smooth external recess extending rearwardly a limited distance behind said dull rear edge portion.
2. In a hollow needle having a lumen of uniform cross section and having a beveled front face providing a lumen opening of cross sectional dimensions no smaller than the cross section of said lumen, said front face including a heel surface behind said lumen opening in said face, said needle having a rounded, smooth and dull edge defining a rear portion of the lumen opening, said heel surface being dished to provide a smooth-surfaced external recess extending rearwardly a limited distance behind said dull rounded edge.
3. A hollow non-coring needle having a lumen of uniform cross section and having a beveled front face providing a lumen opening of cross sectional dimensions no smaller than the cross section of said lumen, said face E also providing a heel surface behind said lumen opening in said face, said heel being externall dished to provide a heel portion of reduced wall thickness, the rear edge portion of said lumen opening adjacent said heel providing a. smooth, rounded and dull surface.
4. A cylindrical hollow needle having a lumen of uniform diameter throughout and having a front face angled with reference to the needles longitudinal axis, said front face being provided with a lumen opening of cross sectional dimensions no smaller than the diameter of said lumen and having a heel surface behind said opening, said heel surface being dished to provide a smooth external recess in the Wall of said needle behind said opening, the rear edge of the lumen opening adjacent said heel being dull and smooth.
5. A cylindrical hollow non-coring needle having a lumen of uniform diameter throughout and having a front face angled with reference to the needles longitudinal axis, said front face providing a lumen opening of cross sectional dimensions no smaller than the diameter of said lumen and having a heel surface behind said opening, the edge portion of the needle about the rear of the lumen opening being elliptical in contour and having a smooth rounded cross-sectional configuration, said heel surface merging with the surface of said edge portion and being dished to provide a smooth-surfaced external recess extending rearwardly a limited distance behind said lumen opening.
6. A non-coring needle having a beveled front face and having a lumen of uniform diameter, said face providing a lumen opening having cross sectional dimensions no smaller than the diameter of said lumen, said face providing behind the lumen opening a heel surface merging with a smooth rounded and dull rear edge portion of said lumen opening, said heel surface being dish-ed to provide a smooth external recess extending rearwardly behind said dull rear edge portion and beyond the outer perimeter of said front face.
7. In a hollow needle having a lumen of uniform cross section and having a beveled front face providing a lumen opening of cross sectional dimensions no smaller than the cross section of said lumen, said front face including a heel surface behind a lumen opening in said face, said needle having a rounded, smooth and dull edge defining a rear portion of the lumen opening, said heel surface being dished to provide a smooth-surfaced external recess extending rearwardly behind said dull rounded edge and beyond the outer perimeter of said front face, said heel surface blending smoothly and gradually into the outer rear surface of said needle beyond the perimeter of said beveled front face.
8. A cylindrical hollow needle having a beveled front face and having a lumen of uniform cross section, said front face providing a lumen opening having cross sectional dimensions no smaller than the cross section of said lumen, said face providing a heel surface behind the lumen opening therein, said heel surface being dished to provide a smooth-surfaced external recess and blending smoothly and gradually into the rear cylindrical surface of said needle beyond the perimeter of said beveled face.
References Cited in the file of this patent UNITED STATES PATENTS 2,560,162 Ferguson July 10, 1951 2,711,733 lacoby June 28, 1955 FOREIGN PATENTS 137,455 Great Britain Ian. 15, 1920 489,535 Canada Ian. 13, 1953